The reverse of support? (7)
I believe the answer is:
backing
I believe this is a double definition.
'the reverse' is the first definition.
(thesaurus)
'support?' is the second definition.
(I know that backing is a type of approval)
'of' is the link.
(Other definitions for backing that I've seen before include "Supporting or betting on" , "Support" , "Endorsement" , "promotion" , "change of wind" .)