Procedure over involuntary movement of the eye (5)
I believe the answer is:
optic
'of the eye' is the definition.
(I've seen this before)
'procedure over involuntary movement' is the wordplay.
'procedure' becomes 'op' (short for operation).
'over' is a charade indicator (letters next to each other).
'involuntary movement' becomes 'tic' (I've seen this before).
'op'+'tic'='OPTIC'
(Other definitions for optic that I've seen before include "Teacher's maybe coming through this" , "Pertaining to the eye" , "connected to the eye" , "bar assistant" , "Teacher's maybe dispensed with this" .)