Greyish-brown grease ruined clothing (9)
I believe the answer is:
dungarees
'clothing' is the definition.
(I know that dungarees is a type of pant)
'greyish-brown grease ruined' is the wordplay.
'greyish-brown' becomes 'dun' (I've seen this before).
'ruined' is an anagram indicator.
'grease' anagrammed gives 'garees'.
'dun'+'garees'='DUNGAREES'
(Other definitions for dungarees that I've seen before include "Durable overalls" , "Hard-wearing work trousers with a bib" , "overalls required" , "Overalls of cotton fabric" , "Worker's trousers with a bib" .)