Dubiously-required double protection (4)
(Other definitions for belt and braces that I've seen before include "Way of giving double chance of success" , "Policy of twofold security?" , "Giving double security" , "Providing double security" , "Doubly safe option" .)
(Other definitions for belt that I've seen before include "Article of clothing" , "Karate insignia of rank" , "sock or > tie" , "Strap" , "Race" .)