Not to mention the claw, in general sheathed (3,5)
I believe the answer is:
let alone
'not to mention' is the definition.
(both can be used to refer to another point)
'claw in general sheathed' is the wordplay.
I cannot quite understand how this works, but
'claw' could be 'talon' (talon is a kind of claw) and 'talon' is present in the answer.
'general' could be 'lee' (Robert E. Lee - US revolutionary commander) and 'lee' is found in the leftover letters.
No letters remain.
This explanation may well be incorrect...
'the' acts as a link.
Can you help me to learn more?
(Other definitions for let alone that I've seen before include "Don't touch" , "Don't bother someone - allow to be solitary" , "Not to mention (thing)" , "Not to mention - much less - avoid" , "Not to mention, never mind" .)