Keeps the best in a large vessel (5)
I believe the answer is:
stops
'keeps' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Perhaps there's a link between them I don't understand?
'the best in a large vessel' is the wordplay.
'the best' becomes 'top' (I've seen this before).
'in' means one lot of letters goes inside another.
'a large vessel' becomes 'ss' (I am not sure about the 'large' bit.).
'top' placed inside 'ss' is 'STOPS'.
Can you help me to learn more?
(Other definitions for stops that I've seen before include "Prevents" , "Posts (anag.)" , "Discontinues" , "Halts" , "Ends" .)