A little bird doing no good (2,2)
I believe the answer is:
at it
'doing no good' is the definition.
I know nothing about this answer so I cannot tell whether this works.
'a little bird' is the wordplay.
'little bird' becomes 'tit' (I've seen this in another clue).
'a'+'tit'='AT IT'
Can you help me to learn more?
(Other definitions for at it that I've seen before include "engaged in dubious activity?" , "Up to no good" , "engaged in crime?" , "Busy" , "Active" .)