Trap I've set for soldier (7)
I believe the answer is:
private
'for soldier' is the definition.
(private is a type of soldier)
'trap i've set' is the wordplay.
'set' is an anagram indicator (instruction to set the letters).
'trap'+'ive'='trapive'
'trapive' anagrammed gives 'PRIVATE'.
(Other definitions for private that I've seen before include "retiring" , "Secret - soldier of the lowest rank" , "Small missile; tuck" , "Not open to scrutiny" , "ranker" .)