Stop publicity prior to competition? (7)
I believe the answer is:
prevent
'stop' is the definition.
(stop can mean to prevent something)
'publicity prior to competition?' is the wordplay.
'publicity' becomes 'PR' (abbreviation for public relations).
'prior to' is a charade indicator (letters next to each other).
'competition?' becomes 'event' (sporting event).
'pr'+'event'='PREVENT'
(Other definitions for prevent that I've seen before include "Keep from happening" , "Obviate" , "Bar" , "Stop, avert" , "Keep from arising" .)