Woman I grumble about (5)
I believe the answer is:
naomi
'woman' is the definition.
'i grumble about' is the wordplay.
'grumble' becomes 'moan' (I've seen this before).
'about' is a reversal indicator.
'i'+'moan'='imoan'
'imoan' backwards is 'NAOMI'.
(Other definitions for naomi that I've seen before include "Biblical woman" , "OT female" , "Ruth's mother-in-law (OT)" , "Girl" , "Biblical mother-in-law of Ruth" .)