Attribute to a writer (7)
I believe the answer is:
ascribe
'attribute to a writer' is the definition.
(I've seen this in another clue)
'a writer' is the wordplay.
'writer' becomes 'scribe' (scribe is a kind of writer).
'a'+'scribe'='ASCRIBE'
(Other definitions for ascribe that I've seen before include "'Impute, assign (7)'" , "Attribute or impute" , "'Attribute, assign (7)'" , "Attribute or credit to" , "Attribute to specified source or cause" .)