American adult caught in trap once more (5)
I believe the answer is:
again
'once more' is the definition.
(synonyms)
'american adult caught in trap' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'adult' becomes 'a' (abbreviation).
'caught in' is an insertion indicator.
'trap' becomes 'gin' (gin trap is a kind of animal trap).
'a' placed into 'gin' is 'gain'.
'a'+'gain'='AGAIN'
(Other definitions for again that I've seen before include "return" , "second term" , "Ocne more" , "One more time, encore" , "Here we go ___" .)