Work stoppage is a hit (6)
I believe the answer is:
strike
This clue is a double definition.
'work stoppage' is the first definition.
(synonyms)
'a hit' is the second definition.
('strike' can be a synonym of 'hit')
'is' is the link.
(Other definitions for strike that I've seen before include "Hit out in industrial dispute" , "Attack - industrial action" , "Everyone out" , "Hit; withdraw labour" , "Hit at a trade dispute" .)