Seven-act plays comprising run for writer (9)
I believe the answer is:
cervantes
'writer' is the definition.
(Miguel de Cervantes)
'seven-act plays comprising run' is the wordplay.
'plays' is an anagram indicator.
'comprising' is an insertion indicator.
'run' becomes 'r' (cricket abbreviation).
'seven'+'act'='sevenact'
'sevenact' is an anagram of 'cevantes'.
'cevantes' enclosing 'r' is 'CERVANTES'.
'for' acts as a link.
(Other definitions for cervantes that I've seen before include "Bookmaker" , "Author of the novel 'Don Quixote'" , "Spanish writer" .)