Zero employment current in York (4)
I believe the answer is:
ouse
'current in york' is the definition.
(river that flows through York)
'zero employment' is the wordplay.
'zero' becomes 'O' (O resembles 0).
'employment' becomes 'use' (how something is used).
'o'+'use'='OUSE'
(Other definitions for ouse that I've seen before include "bird has lost its tail" , "River of 1 across" , "Name of river in Sussex or Yorkshire" , "Runner" , "Flowing water" .)