Keeps the best in a large vessel (5)
I believe the answer is:
stops
'keeps' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Maybe you can see an association between them that I can't see?
'best in a large vessel' is the wordplay.
'best' becomes 'top' (top can mean the very best).
'in' means one lot of letters goes inside another.
'a large vessel' becomes 'ss' (prefix in ship names eg SS Great Britain. I am not sure about the 'large' bit.).
'top' going inside 'ss' is 'STOPS'.
'the' is the link.
Can you help me to learn more?
(Other definitions for stops that I've seen before include "Prevents" , "Posts (anag.)" , "Discontinues" , "Halts" , "Ends" .)