Allow space to put heading (7)
I believe the answer is:
entitle
'allow' is the definition.
(I've seen this before)
'space to put heading' is the wordplay.
'space' becomes 'en' (in printing, a space as wide as a letter 'n').
'to put' is a charade indicator (letters next to each other).
'heading' becomes 'title' (title is a kind of heading).
'en'+'title'='ENTITLE'
(Other definitions for entitle that I've seen before include "Name; empower" , "Furnish with a right or claim" , "Name; enable" , "Call; permit" , "Give a right or authority to" .)