1940s fashion spot admits us too on reflection (4,4)
I believe the answer is:
zoot suit
'1940s fashion' is the definition.
(I've seen this in another clue)
'spot admits us too on reflection' is the wordplay.
'spot' becomes 'zit' (spot on one's body).
'admits' indicates putting letters inside.
'on reflection' shows that the letters should be reversed in order.
'us'+'too'='ustoo'
'ustoo' back-to-front is 'ootsu'.
'zit' enclosing 'ootsu' is 'ZOOT SUIT'.
(Other definitions for zoot suit that I've seen before include "Flashy 1940s' item of menswear" , "Spiv's flashy attire" , "Popular menswear in 1940s' USA" , "retro gear" , "1940s' style of jacket with padded shoulders and tapering trousers" .)