Item of military dress worn mostly flush (7)
I believe the answer is:
baldric
'item of military dress' is the definition.
(type of belt worn by a soldier)
'worn mostly flush' is the wordplay.
'worn' becomes 'bald' (bald can mean worn away).
'mostly' means to remove the last letter (most but not all of the word).
'flush' becomes 'rich' (similar in meaning).
'rich' with its final letter removed is 'ric'.
'bald'+'ric'='BALDRIC'
(Other definitions for baldric that I've seen before include "is under one's belt" , "Edmund's servant" , "Sword-belt" , "Carrier for weapon" , "Sword belt" .)