Stimulant - reason for dregs (6,7)

I believe the answer is:

coffee grounds

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'dregs' is the definition.
(coffee grounds is a kind of dregs)

'stimulant reason' is the wordplay.
'stimulant' becomes 'coffee' (I can't explain this - if you can you should give a lot more credence to this answer).
'reason' becomes 'grounds' (grounds or justification for a particular action).
'coffee'+'grounds'='COFFEE GROUNDS'

'for' is the link.

Can you help me to learn more?

(Other definitions for coffee grounds that I've seen before include "Consequence of perks" , "Result of drink" , "Residue in percolator" , "Espresso dregs?" .)

I've seen this clue in The Daily Express.

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