Last month identity revealed by editor settled it (7)
I believe the answer is:
decided
'last' is the definition.
Both the definition and answer are adjectives. Perhaps you can see a link between them that I can't see?
'month identity revealed by editor settled it' is the wordplay.
I cannot quite see how this works, but
'month' could be 'dec' (abbreviation for December) and 'dec' is found in the answer.
'identity' could be 'id' (abbreviation) and 'id' is present in the answer.
'editor' could be 'ed' (abbreviation) and 'ed' is found within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for decided that I've seen before include "Made mind up, being unequivocal" , "unmistakable" , "Categorical" , "Made up one's mind" , "Came to a resolution" .)