Replacin' the soundtrack for Grease (6)
I believe the answer is:
dubbin
This clue is a double definition.
'replacin' the soundtrack' is the first definition.
('dubbing' with the 'g' dropped)
'grease' is the second definition.
(type of grease)
'for' is the link.
(Other definitions for dubbin that I've seen before include "Tallow mixture used to make leather waterproof" , "Grease for softening leather" , "It's used to make leather soft and waterproof" , "Thick grease for water-proofing leather" .)