Succeeded, as things are, to halt flow from peak (7)
I believe the answer is:
snowcap
'peak' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's a link between them I don't understand?
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for snowcap that I've seen before include "mountain region" , "that may come to a peak" , "Winter summit" , "result of fall on mountain" , "White top on mountain" .)