Go mad, given failure to find sandal (4-4)
I believe the answer is:
flip-flop
'sandal' is the definition.
(I have seen 'Flimsy sandal ' mean 'flip-flop' so perhaps 'sandal' could also mean 'flip-flop')
'go mad given failure' is the wordplay.
'go mad' becomes 'flip' (I've seen this before).
'given' is a charade indicator (letters next to each other).
'failure' becomes 'flop' (flop is a kind of failure).
'flip'+'flop'='FLIP-FLOP'
'to find' acts as a link.
(Other definitions for flip-flop that I've seen before include "Rubber-soled sandal" , "Light shoe" , "Flimsy sandal" , "Rubber sandal" , "Informal footwear" .)