It helps tramp perhaps to settle down (7)
I believe the answer is:
ballast
This could be a double definition.
'it helps tramp perhaps' is the first definition.
The definition suggests a singular noun which matches the answer.
'settle down' is the second definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I don't see?
'to' is the link.
Can you help me to learn more?
(Other definitions for ballast that I've seen before include "Lab salt (anag.)" , "Material for railway bed" , "Heavy stuff used to stabilise boat" , "Mass giving ship stability" , "Counterweight" .)