Understood reversed article to be ancient dress (4)
I believe the answer is:
toga
'ancient dress' is the definition.
'toga' can be an answer for 'dress' (I have seen 'Roman dress ' mean 'toga' so perhaps 'dress' could also mean 'toga'). I am unsure of the 'ancient' bit.
'understood reversed article' is the wordplay.
'understood' becomes 'got' (getting is a kind of understanding).
'reversed' shows that the letters should be reversed in order.
'article' becomes 'a' (the indefinite article in English).
'got' backwards is 'tog'.
'tog'+'a'='TOGA'
'to be' is the link.
Can you help me to learn more?
(Other definitions for toga that I've seen before include "Got a robe for an old Roman" , "Roman tunic" , "Graph's y value" , "Got a cloak for an old Roman" , "Robe worn by Caesar" .)