Relating to nerves (6)
I believe the answer is:
neural
'relating to nerves' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for neural that I've seen before include "Relating to a nerve" , "Relating to the nervous system" , "Nervy" , "Relating to nerves" , "To do with nerve of unreal kind" .)