Vehicle driver heading off to board Yankee vessel (6)
I believe the answer is:
artery
'vehicle driver' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'heading off to board yankee vessel' is the wordplay.
'heading off' means to remove the first letter.
'to board' becomes 'dart' (dart board is a kind of board).
'yankee vessel' becomes 'ery' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'dart' with its initial letter taken off is 'art'.
'art'+'ery'='ARTERY'
Can you help me to learn more?
(Other definitions for artery that I've seen before include "Main traffic route" , "Principle channel of circulatory system" , "Vital tube" , "Major traffic route" , "bloody path" .)