One left with snake sat round in vessel (8)

'vessel' is the definition.
(I know that Sailboat is a type of sailing ship)

'one left with snake sat round' is the wordplay.
I cannot quite see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'left' could be 'al' (I've seen this in other clues) and 'al' is present in the remaining letters.
'snake' could be 'boa' (boa is a kind of snake) and 'boa' is located in the answer.
The remaining letters 'st' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

'in' acts as a link.

Can you help me to learn more?