Diablo useful to display garment (6)
I believe the answer is:
blouse
'garment' is the definition.
(blouse is a kind of garment)
'diablo useful to display' is the wordplay.
'to display' says the answer is hidden in the clue (I've seen 'displaying' mean this).
'BLOUSE' is hidden within 'diablo useful'.
(Other definitions for blouse that I've seen before include "Obelus (anag) - buttoned top" , "Woman's buttoned top" , "Ladies' top" , "Within a building" , "Woman's "shirt"" .)