Stock tune (6)
I believe the answer is:
strain
This clue is a double definition.
'stock' is the first definition.
(I know that stock can be written as strain)
'tune' is the second definition.
(I know that tune can be written as strain)
(Other definitions for strain that I've seen before include "Blood" , "Overtax; tension" , "Filter - intense effort" , "Family; effort" , "Pressure - filter" .)