Travelling Martian bearing right in vessel (8)
I believe the answer is:
trimaran
'vessel' is the definition.
(trimaran is a kind of vessel)
'travelling martian bearing right' is the wordplay.
'travelling' indicates an anagram.
'bearing' indicates putting letters inside.
'right' becomes 'r' (common abbreviation).
'martian' is an anagram of 'timaran'.
'timaran' enclosing 'r' is 'TRIMARAN'.
'in' is the link.
(Other definitions for trimaran that I've seen before include "Sailing vessel" , "Sailing boat with 3 hulls" , "Three-hulled vessel" , "type of boat" , "Three-hulled boat" .)