But they don't smooth out the sea roads (7)
I believe the answer is:
rollers
'roads' is the definition.
The definition and answer can be both acts as well as being plural nouns.
Maybe there's an association between them I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for rollers that I've seen before include "expensive cars" , "Long heavy sea waves" , "They may be used to paint" .)