Vessel and vehicle needed by old king (6)
I believe the answer is:
canute
'old king' is the definition.
(medieval Danish king)
'vessel and vehicle needed by' is the wordplay.
'vessel' becomes 'can' (I've seen this before).
'and' is a charade indicator (letters next to each other).
'vehicle' becomes 'ute' (Australian abbreviation for utility vehicle).
'needed' says to put letters next to each other.
'by' means one lot of letters go next to another.
'can'+'ute'='CANUTE'
(Other definitions for canute that I've seen before include "English king who ordered waves to retreat" , "Ancient king who ordered the waves to retreat" , "King of England, Denmark and Norway" , "The king who thought he could stop the tide" , "Old king of England who tried to stop the tide" .)