Bird out at sea ahead of vessel (6)
I believe the answer is:
toucan
'bird' is the definition.
(toucan is a kind of bird)
'out at sea ahead of vessel' is the wordplay.
'at sea' is an anagram indicator.
'ahead of' says to put letters next to each other (I've seen this in other clues).
'vessel' becomes 'can' (I've seen this before).
'out' with letters rearranged gives 'tou'.
'tou'+'can'='TOUCAN'
(Other definitions for toucan that I've seen before include "Tropical American bird with immense beak" , "Showy bird" , "exotic bird" , "One with huge bill" , "Brightly-coloured tropical bird with large beak" .)