Keeps a ship going round a river (5)
I believe the answer is:
stays
'keeps' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Perhaps you can see a link between them that I don't see?
'a ship going round a river' is the wordplay.
'a ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'going round' means one lot of letters goes inside another (some letters go around others).
'a river' becomes 'tay' (Scottish river).
'ss' enclosing 'tay' is 'STAYS'.
Can you help me to learn more?
(Other definitions for stays that I've seen before include "Boards, lodges" , "for a slimmer figure" , "Remains (in place)" , "Puts up with" , "Supports" .)