Wake up after midnight and moan (6)
I believe the answer is:
grouse
'moan' is the definition.
(thesaurus)
'wake up after midnight' is the wordplay.
'wake up' becomes 'rouse' (I've seen this before).
'after' is a charade indicator (letters next to each other).
'midnight' becomes 'g'.
'rouse' put after 'g' is 'GROUSE'.
'and' is the link.
(Other definitions for grouse that I've seen before include "The complaint of a gamebird" , "See game bird" , "Complain like gamebird" , "Complain pettily" , "Plump game bird" .)