Imitate large bird after midnight, say (7)
I believe the answer is:
emulate
'imitate' is the definition.
(I know that emulate is a more specific form of the action imitate)
'large bird after midnight say' is the wordplay.
'large bird' becomes 'emu' (I've seen this before).
'after midnight say' becomes 'late' (I've seen this in another clue).
'emu'+'late'='EMULATE'
(Other definitions for emulate that I've seen before include "Try to match" , "Ape" , "Follow in the footsteps of" , "Copy -- reach equality with" , "Strive to equal or match" .)