Type of sandal (4-4)
'type of sandal' is the definition.
(I know that Flip-flop is a type of sandal)
This is the entire clue.
(Other definitions for flip-flop that I've seen before include "Flimsy sandal" , "Shoe held on by a toe-thong" , "Rubber sandal" , "Sandal held on by a toe-thong" , "Informal footwear" .)