Came by to return a garment (4)
I believe the answer is:
toga
'garment' is the definition.
(toga is a kind of garment)
'came by to return a' is the wordplay.
'came by' becomes 'got' (I've seen this in another clue).
'to return' says the letters should be written in reverse.
'got' back-to-front is 'tog'.
'tog'+'a'='TOGA'
(Other definitions for toga that I've seen before include "Robe for an ancient Roman" , "garment of old" , "Roman tunic" , "piece of old clothing" , "Garment worn by men in ancient Rome" .)