Disincentive of French shelter to take stray (9)
I believe the answer is:
deterrent
'disincentive' is the definition.
(I've seen this before)
'of french shelter to take stray' is the wordplay.
'of french' becomes 'de' ('of' in French).
'shelter' becomes 'tent' (canvas shelter).
'to take' means one lot of letters goes inside another (inserted letters are taken in).
'stray' becomes 'err' (to err is to stray or go wrong).
'tent' placed around 'err' is 'terrent'.
'de'+'terrent'='DETERRENT'
(Other definitions for deterrent that I've seen before include "Nuclear weapons allegedly" , "Discouragement, disincentive" , "Something designed to be off-putting" , "Something that puts people off" , "Something discouraging action" .)