Left first eagle talon free finally; allow to be undisturbed (3,5)
I believe the answer is:
'to be undisturbed' is the definition.
'left first eagle talon free finally' is the wordplay.
'left' becomes 'l' (common abbreviation).
'first eagle' becomes 'e' (1st letter of 'eagle').
'finally' indicates one should take the final letters.
The last letter of 'free' is 'e'.
'allow' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for let alone that I've seen before include "Not to mention - much less - avoid" , "Not to mention, never mind" , "Don't touch" , "Don't bother someone - allow to be solitary" , "Not to mention (thing)" .)