Summer blouse (6)
I believe the answer is:
halter
'summer blouse' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for halter that I've seen before include "Part of harness" , "Headgear for leading a horse" , "Rope or canvas on a horse's head" , "Leather strap for leading a horse" , "When there's harness" .)