A Poet Laureate perhaps crossing over on a ship (6)
I believe the answer is:
aboard
'on a ship' is the definition.
(I've seen this before)
'a poet laureate perhaps crossing over' is the wordplay.
'poet laureate perhaps' becomes 'bard'.
'crossing' means one lot of letters goes inside another.
'over' becomes 'o' (cricket abbreviation**).
'bard' going around 'o' is 'board'.
'a'+'board'='ABOARD'
(Other definitions for aboard that I've seen before include "Part of the group" , "on a plane, perhaps" , "on boat, perhaps" , "on a ferry?" , "On an aircraft" .)