Whinge (5)
(Other definitions for gripe that I've seen before include "Grievance" , "beef" , "Complain; colic (water)" , "Keep on complaining" , "Trivial complaint" .)
'whinge' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for moan that I've seen before include "Murmur of pain; grumble" , "Express pain" , "Complaint" , "Complain; mournful sound" , "Bewail" .)