Check in unrefined earth for pigment (5)
I believe the answer is:
ochre
'pigment' is the definition.
(ochre is a kind of pigment)
'check in unrefined earth' is the wordplay.
'check' becomes 'ch' (I've seen this in other clues).
'in' means one lot of letters goes inside another.
'unrefined earth' becomes 'ore'.
'ch' going into 'ore' is 'OCHRE'.
'for' is the link.
(Other definitions for ochre that I've seen before include "Earth coloured pigment" , "Yellow-orange colour" , "natural colouring" , "Yellow/brown/red pigment" , "Yellow/brown pigment" .)