Being a bird, it’s after seed (5)
I believe the answer is:
pipit
'being a bird it's after seed' is the definition.
I can't tell whether this definition defines the answer.
'it's after seed' is the wordplay.
'it's' becomes 'it' (I've seen this in other clues**).
'after' is a charade indicator (letters next to each other).
'seed' becomes 'pip' (I've seen this before).
'it' put after 'pip' is 'PIPIT'.
(Other definitions for pipit that I've seen before include "Lark-like songbird" , "Songbird of open country" , "Bird of meadow, tree, or rock" , "Lark-like bird" , "Songbird of rock or meadow" .)