A fairly straightforward Jumbo, I thought, with quite a high proportion of double definitions/indications. A few of the answers - possibly ALCALDE, CICERONE, PENEPLAIN - may not be familiar to everyone, but they're in most of the standard dictionaries.
As usual, * indicates an anagram.
| Across |
| 1 | ANTELOPE - ELOPE after ANT |
| 5 | DRIFTS - RIFT between D and S |
| 9 | BEEF TEA - BEE + FT (Financial Times) + Enjoy + A |
| 14 | CHAMBERMAID - CHARM + AID, around MBE |
| 15 | LOUTISHNESS - (he insults so)* |
| 16 | LASER - LA'S, + ER (Queen Elizabeth, hence 'top woman') |
| 17 | AFGHANI - A + F + GHANa + I |
| 18 | RATTLES ON - RATTLE SON |
| 19 | EXAMINE - axe (reversed) + MINE |
| 20 | PLOUGHMAN'S LUNCH - cryptic definition. 'Traditional' may describe a ploughman who uses a (plough)share, but the term itself, describing a meal of bread, cheese and chutney, was apparently dreamt up in the 1950s by the British Cheese Bureau |
| 22 | PRESENT-DAY - PAY, around RESENT + rewarD |
| 23 | THWART - THe + WAR + thaT |
| 25 | CUBE - CUB + E |
| 28 | AS THE CASE MAY BE - double definition |
| 30 | SKIN-DEEP - KIND in SEEP |
| 32 | CICERONE - ICE in CRONE |
| 34 | COLLECTIVE NOUN - cryptic definition (school is the COLLECTIVE NOUN used for many types of fish, i.e. 'swimmers') |
| 37 | BORE - B + ORE, and double definition ('hole'; 'not something of interest') |
| 38 | TORERO - TORE, + OR (other ranks), reversed |
| 39 | IONOSPHERE - (here poison)* |
| 43 | FINISHING SCHOOL - double definition |
| 45 | LONG LEG - double definition. Yes, it's this week's cricketing clue |
| 47 | ENROLMENT - E + NR + O, + LT (lieutenant) around MEN |
| 49 | OCARINA - hidden in turbOCAR INActive |
| 51 | PETAL - Prose + ET AL (short for 'et alia', indicated by 'other writers') |
| 52 | DON GIOVANNI - (vain doing no)* |
| 53 | SECRET AGENT - SENT, around CRETE around AG (symbol for the element silver) |
| 54 | SLENDER - S + LENDER |
| 55 | DIGEST - double definition |
| 56 | STANDS IN - STAND SIN |
| Down |
| 1 | ALCALDE - AL (Capone), + C, + (deal)* |
| 2 | TRANSPARENT - A + N + SPA, in TRENT |
| 3 | LIBERTINE - BERT + I, in LINE |
| 4 | PERMANENT MAGNET - cryptic definition |
| 6 | RADIATOR - RA + DIOR, around heAT |
| 7 | FILLING THE BILL - double definition |
| 8 | SQUARE MEAL - 'mare squeal', indicated by 'horse yelp', would be a Spoonerism of MARE SQUEAL |
| 9 | BRITTEN - joB + wRITTEN |
| 10 | ETHEL - EeL around THE |
| 11 | TREASONABLE - TABLE (indicated by 'move at meeting', as in 'table a motion'), around REASON |
| 12 | ABSINTHE - A + B + SIN + THE |
| 13 | SANG - SlANG |
| 20 | PLANET - PLAN, + ET ('the extra-terrestrial') |
| 21 | LICENSE - (silence)* |
| 22 | PLANCK - sounds like 'plank' |
| 24 | TAKE IT OR LEAVE IT - double indication. IT is short for 'Italian vermouth', which a gin drinker might or might not take |
| 26 | DAY OF RECKONING - double indication |
| 27 | SPONGE - double definition |
| 29 | EARNERS - lEARNERS |
| 31 | SCROLL - double definition |
| 33 | CROWN PRINCE - CROW IN CE (church of England), around N + PR |
| 35 | OPEN LETTERS - (rotten sleep)* |
| 36 | FRIGHTENED - F + RIGHTENED |
| 40 | PENEPLAIN - PEN + LAIN, around EP (extended play record) |
| 41 | EFFENDIS - (stiffened)* |
| 42 | MOLASSES - LASSES, after MO (moment) |
| 44 | ICE OVER - I + COVER around Evening |
| 46 | GELATIN - G + E + LATIN |
| 48 | LAIRD - I in LARD |
| 50 | INCH - IN + CH (in church, hence possibly 'at communion') |