Brown to process leather (3)
I believe the answer is:
tan
This clue is a double definition.
'brown' is the first definition.
(I know that tan is a type of light brown)
'process leather' is the second definition.
(I've seen this in another clue)
'to' acts as a link.
(Other definitions for tan that I've seen before include "Yellow-brown colour" , "belt" , "Nice brown induced by sun" , "Catch the sun" , "function" .)