Permitted degree of subtlety (3)
I believe the answer is:
let
'permitted degree' is the definition.
'let' can be an answer for 'permitted' (to let something happen is to permit it). I'm not sure about the 'degree' bit.
'of subtlety' is the wordplay.
'of' says the answer is hidden in the clue.
'LET' can be found hidden inside 'subtlety'.
Can you help me to learn more?
(Other definitions for let that I've seen before include "Permit or rent" , "Won't stop you" , "& 15 Triple (anag.)" , "Reason for scrubbing service" , "Umpire's decision" .)