Vessels to credit with being potentially fast? (6)
I believe the answer is:
crafts
'vessels' is the definition.
('craft' can be a synonym of 'vessel')
'credit with being potentially fast?' is the wordplay.
'credit' becomes 'cr' (abbreviation).
'with' is a charade indicator (letters next to each other).
'being potentially' indicates an anagram (letters have the potential to spell a new word).
'fast' is an anagram of 'afts'.
'cr'+'afts'='CRAFTS'
'to' is the link.
(Other definitions for crafts that I've seen before include "Skilled trades" , "Activities involving skill in making things by hand" , "Hand-made objects" , "Occupations in which skills are needed" , "Objects made by hand" .)