Paint found beneath garment (9)
I believe the answer is:
undercoat
'paint' is the definition.
(undercoat is a kind of paint)
'beneath garment' is the wordplay.
'beneath' becomes 'under' (under means beneath or underneath).
'garment' becomes 'coat' (coat is a kind of garment).
'under'+'coat'='UNDERCOAT'
'found' is the link.
(Other definitions for undercoat that I've seen before include "tin of paint?" , "The first layer of paint" .)