Tilt when boarding does for vessel (8)
I believe the answer is:
decanter
'vessel' is the definition.
(decanter is a kind of vessel)
'tilt when boarding does' is the wordplay.
'tilt' becomes 'cant' (synonyms).
'when boarding' means one lot of letters goes inside another.
'does' becomes 'deer' (I've seen this in other clues).
'cant' put within 'deer' is 'DECANTER'.
'for' acts as a link.
(Other definitions for decanter that I've seen before include "bottle needed" , "Ornamental bottle for dispensing wine" , "glass full of drink" , "Wine/spirits container" , "Ornamental bottle into which wine is poured slowly" .)