A governing body on a ship (6)
I believe the answer is:
aboard
'on a ship' is the definition.
(I've seen this before)
'a governing body' is the wordplay.
'governing body' becomes 'board' (I've seen this in another clue).
'a'+'board'='ABOARD'
(Other definitions for aboard that I've seen before include "Embarked on (a ship)" , "on boat, perhaps" , "Joined for mutual benefit" , "on a train, perhaps" , "on a liner, say" .)