Girl is going west for brown pigment (6)
I believe the answer is:
sienna
'brown pigment' is the definition.
(I've seen this in another clue)
'girl is going west' is the wordplay.
'girl' becomes 'anne' (girl's name).
'going west' says the letters should be written in reverse (letters heading to the west or left).
'anne'+'is'='anneis'
'anneis' backwards is 'SIENNA'.
'for' acts as a link.
(Other definitions for sienna that I've seen before include "Browny-yellow pigment" , "Earth colour, may be burnt" , "Earthy colour" , "A shade" , "Yellow-brown clay used in paint pigments" .)