Moderately rich oil producer on holiday (4,3)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

WELL [oil producer] OFF [on holiday] 5 WOLFRAM : WOLF RAM 10 BEAR : double definition 11 DEEP BREATH : cryptic [?] definition 12 ETCHER : cryptic [?] definition] 13 MATTRESS : anagram [form] of SMARTEST 14 WRESTLING : cryptic [?] definition 16 ANDES : AND E S [points] 17 BANNS : BAN [exclude] N S [poles] 19 BE CAREFUL : cryptic definition 23 MEASURES : a hand is ‘a unit of length measuring four inches, used to measure the height of horses’ 24 UMPIRE : cryptic definition, referring to Lord’s cricket ground 26 WITHOUT END : double definition 27 LAGS : double definition 28 TALLY-HO : TALLY [agree] HO[me] 29 TRINITY : I NIT – reversal [turn] of TIN [can] in TRY [essay]: there is a Trinity College at both Oxford and Cambridge