Sets straight on the subject of clothes (9)
I believe the answer is:
Here is my best explanation:
'sets straight' is the definition.
Although both the answer and definition are verbs in their -s form, I don't understand how they can define each other.
'on the subject of clothes' is the wordplay.
'on' says to put letters next to each other.
'the subject of' becomes 're' (I've seen this in other clues).
'clothes' becomes 'dresses' ('dress' can be a synonym of 'clothe').
're' put next to 'dresses' is 'REDRESSES'.
(Other definitions for redresses that I've seen before include "Sets right, makes amends" and "Pays for".)