Soldiers certain to suppress mass resistance and succeed (5)
I believe the answer is:
ensue
'succeed' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for ensue that I've seen before include "Occur as a result (of)" , "Happen afterwards as a result" , "Cultivate plants/vegetables" , "Follow as a consequence" , "Come along afterwards" .)