Lark back in poem again (4)
I believe the answer is:
game
'lark' is the definition.
(I've seen this before)
'back in poem again' is the wordplay.
'back' shows that the letters should be reversed in order.
'in' indicates a hidden word.
'emag' can be found hidden inside 'poem again'.
'emag' written backwards gives 'GAME'.
(Other definitions for game that I've seen before include "Hunted wild animals" , "Willing to try" , "Something to play or to chase" , "Somehow disabled" , "Eager; pastime" .)