Sabotage stock with first cut on fur (9)
I believe the answer is:
undermine
'sabotage' is the definition.
(I know that sabotage can be written as undermine)
'stock with first cut on fur' is the wordplay.
'stock with first cut' becomes 'und' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'on' is a charade indicator (letters next to each other).
'fur' becomes 'ermine' (ermine is a kind of fur).
'und'+'ermine'='UNDERMINE'
Can you help me to learn more?
(Other definitions for undermine that I've seen before include "Erode the base or foundation of" , "Weaken, sap" , "Burrow below" , "Erode foundations" , "Subvert or weaken gradually" .)