Has left behind a paper about clothes (7)
I believe the answer is:
apparel
'clothes' is the definition.
(synonyms)
'has left behind a paper about' is the wordplay.
'has left' becomes 'l' (I am not sure about this - if you are sure you should believe this answer much more).
'behind' says to put letters next to each other.
'about' indicates anagramming the letters.
'paper' with letters rearranged gives 'ppare'.
'a'+'ppare'='appare'
'l' put after 'appare' is 'APPAREL'.
Can you help me to learn more?
(Other definitions for apparel that I've seen before include "it's generally put on!" , "kit" , "Attire" , "what's in the press?" , "Clothes - garments" .)