Some nerve twitching after surgical procedure (5)
I believe the answer is:
optic
'some nerve' is the definition.
(optic nerve is a kind of nerve)
'twitching after surgical procedure' is the wordplay.
'twitching' becomes 'tic' (tic is a kind of twitching).
'after' means one lot of letters go next to another.
'surgical procedure' becomes 'op' (short for operation).
'tic' after 'op' is 'OPTIC'.
(Other definitions for optic that I've seen before include "Like a sort of nerve" , "Pertaining to the eye" , "Visual" , "Device for measuring out spirits" , "Pub measure" .)