Biblical mother-in-law I complain about (5)
I believe the answer is:
naomi
'biblical mother-in-law' is the definition.
(I've seen this in another clue)
'i complain about' is the wordplay.
'complain' becomes 'moan' (moan can mean to complain or whinge).
'about' says the letters should be written in reverse.
'i'+'moan'='imoan'
'imoan' back-to-front is 'NAOMI'.
(Other definitions for naomi that I've seen before include "Ruth's mother-in-law (Old Testament)" , "Biblical woman" , "Biblical character" , "woman's name" , "woman in the Bible" .)