Stop extremely popular occurrence (7)
I believe the answer is:
prevent
'stop' is the definition.
(stop can mean to prevent something)
'extremely popular occurrence' is the wordplay.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'occurrence' becomes 'event' (I've seen this in another clue).
'popular' with its middle removed is 'pr'.
'pr'+'event'='PREVENT'
(Other definitions for prevent that I've seen before include "Obviate" , "Stop from happening" , "Stop, hinder" , "Keep from happening" , "Keep from arising" .)