Enemy caught by Tasmanian tiger (4)
I believe the answer is:
anti
'enemy' is the definition.
(thesaurus)
'caught by tasmanian tiger' is the wordplay.
'caught by' indicates a hidden word.
'ANTI' can be found hidden inside 'tasmanian tiger'.
(Other definitions for anti that I've seen before include "not favoured" , "Opposition member" , "Prefix meaning against" , "[NO MAN]" , "Someone opposed (to a policy?)" .)