Goes after a companion on the wild seas (6)
I believe the answer is:
chases
'goes after' is the definition.
('chase' can be a synonym of 'go after')
'a companion on the wild seas' is the wordplay.
'a companion' becomes 'ch' (Companion of Honour).
'on' indicates putting letters inside.
'the wild' is an anagram indicator.
'seas' is an anagram of 'ases'.
'ch' going into 'ases' is 'CHASES'.
(Other definitions for chases that I've seen before include "Follows in order to catch" , "performs follow-up" , "Pursues or follows" , "Runs after, pursues" .)