Strong wind ripped advert off, initially (7)
I believe the answer is:
tornado
'strong wind' is the definition.
(I've seen this before)
'ripped advert off initially' is the wordplay.
'ripped' becomes 'torn' ('torn' can be a synonym of 'ripped').
'advert' becomes 'ad' ('ad' can be a synonym of 'advert').
'initially' suggests taking the first letters.
The initial letter of 'off' is 'o'.
'torn'+'ad'+'o'='TORNADO'
(Other definitions for tornado that I've seen before include "Major storm" , "This is quite a blow" , "Funnel-shaped windstorm" , "Destructive wind vortex" , "Severe wind" .)