More than one work stoppage makes an impact (7)
I believe the answer is:
strikes
This clue might be a double definition.
'more than one work stoppage' is the first definition.
('strike' can be a synonym of 'work stoppage')
'makes an impact' is the second definition.
'strikes' can be an answer for 'makes' (striking is a kind of making). I'm not sure about the 'an impact' bit.
Can you help me to learn more?
(Other definitions for strikes that I've seen before include "(Takes) industrial action" , "Impresses" , "Hits" .)