Boat company in Cornwall etc. (4)
I believe the answer is:
scow
'boat' is the definition.
(scow is a kind of boat)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for scow that I've seen before include "Vessel" , "Maybe lighter" , "Low boat" , "ighter" , "Unpowered freight barge" .)