Earlier, the companion boarded the vessel (8)
I believe the answer is:
schooner
'the vessel' is the definition.
(type of ship)
'earlier the companion boarded' is the wordplay.
I cannot really see how this works, but
'companion' could be 'ch' (Companion of Honour) and 'ch' is found in the answer.
'earlier' could be 'sooner' (synonyms) and 'sooner' is found in the remaining letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for schooner that I've seen before include "Swift sailing vessel - sherry glass" , "boat" , "No chores on this sailing ship" , "A measure or glass for sherry" , "Sailing vessel - drinking vessel" .)