I leave fast before a complaint (7)
I believe the answer is:
lentigo
'a complaint' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see a link between them that I don't see?
'i leave fast before' is the wordplay.
'leave' becomes 'go'.
'fast' becomes 'lent' (Lent is a period of fasting in Christianity).
'before' says to put letters next to each other.
'i'+'go'='igo'
'igo' after 'lent' is 'LENTIGO'.
Can you help me to learn more?
(Other definitions for lentigo that I've seen before include "skin discoloration" , "Spots" , "Technical name for a freckle" , "Skin condition" , "Skin disease" .)