Paintings in works defaced (4)
I believe the answer is:
oils
'paintings' is the definition.
(I've seen this before)
'works defaced' is the wordplay.
'works' becomes 'toils' (toil is a kind of work).
'defaced' means to remove the first letter (the word with its face removed).
'toils' with its first letter removed is 'OILS'.
'in' is the link.
(Other definitions for oils that I've seen before include "Olive and sesame, for instance" , "Painting medium" , "Reduces friction" , "Liquids for frying" , "Viscous substances kept in silo" .)