Second person caught sheep (3)
I believe the answer is:
ewe
'sheep' is the definition.
(a ewe is a female sheep)
'second person caught' is the wordplay.
'second person' becomes 'you' (second person pronoun).
'caught' indicates a 'sounds like' (homophone) clue (heard).
'you' is a homophone of 'EWE'.
(Other definitions for ewe that I've seen before include "Scottish loch" , "Source of milk" , "Language" , "creature" , "Female in a fleece?" .)