One snake seized by bats etc in vessel (7)
I believe the answer is:
iceboat
'vessel' is the definition.
(iceboat is a kind of vessel)
'one snake seized by bats etc' is the wordplay.
'one' becomes 'i' (Roman numeral).
'snake' becomes 'boa' (boa is a kind of snake).
'seized by' means one lot of letters goes inside another.
'bats' indicates anagramming the letters (I've seen this in other clues).
'etc' anagrammed gives 'cet'.
'boa' placed inside 'cet' is 'ceboat'.
'i'+'ceboat'='ICEBOAT'
'in' acts as a link.
(Other definitions for iceboat that I've seen before include "Arctic vessel" , "it cuts through arctic seas" , "Ship used to clear way in polar waters" , "One'll break through the pack" , "Craft" .)