It's worn to order perhaps (4)
I believe the answer is:
sash
'order perhaps' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'it's worn' is the wordplay.
'it's' becomes 'sa's' (old-fashioned abbreviation for sex appeal).
'worn' becomes 'h' (I am not sure about this - if you are sure you should believe this answer much more).
'sas'+'h'='SASH'
'to' is the link.
Can you help me to learn more?
(Other definitions for sash that I've seen before include "Brown bread for waist or shoulder" , "Band of cloth" , "Baldrick" , "Cummerbund" , "seen hanging around Miss World?" .)