Unfeeling member very posh girl rejected (4,3)
I believe the answer is:
dead leg
'unfeeling member' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'very posh girl rejected' is the wordplay.
'very' becomes 'dead' (dead can mean very or absolutely, eg 'dead wrong').
'posh girl' becomes 'gel' (I've seen this in other clues).
'rejected' is a reversal indicator.
'gel' written backwards gives 'leg'.
'dead'+'leg'='DEAD LEG'
Can you help me to learn more?
(Other definitions for dead leg that I've seen before include "impact injury" , "Temporary numbness in a lower limb, after a hit" , "Temporary affliction" .)