Senate garb (4)
I believe the answer is:
toga
'senate garb' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for toga that I've seen before include "Graph's y value" , "Ancient Roman garment" , "Outer garment" , "Roman gents' cloak" , "Garment worn by men in ancient Rome" .)