Clothes appear wrong when put on a number (7)
I believe the answer is:
apparel
'clothes' is the definition.
(synonyms)
'appear wrong when put on a number' is the wordplay.
'wrong' is an anagram indicator.
'when put on' means one lot of letters go next to another (in a down clue, some letters go on top of others).
'a number' becomes 'L' (fifty in Roman numerals).
'appear' with letters rearranged gives 'appare'.
'appare'+'l'='APPAREL'
(Other definitions for apparel that I've seen before include "Clothes - garments" , "Raiment" , "Pod of peas" , "it's generally put on!" , "Fancy gear" .)