Feline from many centuries ago found in sailing vessel (6)
I believe the answer is:
bobcat
'feline' is the definition.
(bobcat is a kind of feline)
'from many centuries ago found in sailing vessel' is the wordplay.
'from many centuries ago' becomes 'BC' (Before Christ).
'found in' is an insertion indicator.
'sailing vessel' becomes 'boat' (sailing boat).
'bc' going within 'boat' is 'BOBCAT'.
(Other definitions for bobcat that I've seen before include "Type of lynx" , "Small lynx of Norht America" , "Relation of the lynx" , "North American feline" , "Kind of lynx" .)