Vessel -- and what might go under one (7)
I believe the answer is:
coaster
'vessel' is the definition.
(I've seen this before)
'what might go under one' is the wordplay.
I cannot really see how this works, but
'one' could be 'a' and 'a' is located in the answer.
The remaining letters 'coster' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'and' acts as a link.
Can you help me to learn more?
(Other definitions for coaster that I've seen before include "Tray; trader" , "Mat for decanter or glasses" , "Small table mat" , "Small ship or beer mat" , "Trading vessel" .)