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" .)

I've seen this clue in The Globe and Mail, The Irish News and The Independent.

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