Unusual cut in garment (5)
I believe the answer is:
tunic
'garment' is the definition.
(historical type of garment)
'unusual cut in' is the wordplay.
'unusual' is an anagram indicator.
'cut'+'in'='cutin'
'cutin' is an anagram of 'TUNIC'.
(Other definitions for tunic that I've seen before include "Roman garment" , "Close-fitting jacket that's part of a uniform" , "Shift" , "Loose sleeveless garment" , "Simple garment" .)