Unusual cut in garment (5)
'garment' is the definition.
(historical type of garment)
'unusual cut in' is the wordplay.
'unusual' is an anagram indicator.
'cutin' anagrammed gives 'TUNIC'.
(Other definitions for tunic that I've seen before include "School garment", "Loose-fitting shirt or cloak", "Schoolgirl's dress", "Knee-length cloak", "Jacket of some soldiers".)