Weaken juice (3)

I believe the answer is:

sap

I believe this clue is a double definition.

'weaken' is the first definition.
(thesaurus)

'juice' is the second definition.
(thesaurus)

(Other definitions for sap that I've seen before include "It's plant juice, idiot" , "Undermine; fool" , "Enervate" , "Fluid in plant stem" , "Watery substance in plants" .)

I've seen this clue in The Times.

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