A trap set outside a second time (5)
I believe the answer is:
again
'second time' is the definition.
(again means for a second time)
'a trap set outside a' is the wordplay.
'trap set' becomes 'gin' (I am not sure about this - if you are sure you should believe this answer much more).
'outside' indicates putting letters inside (some letters go outside others).
'gin' going around 'a' is 'gain'.
'a'+'gain'='AGAIN'
Can you help me to learn more?
(Other definitions for again that I've seen before include "'Another time, once more (5)'" , "10 10 [AGAIN" , "return" , "Anew" , "repeat order" .)