Broken oar bad on ship (6)
I believe the answer is:
aboard
'on ship' is the definition.
(I've seen this before)
'broken oar bad' is the wordplay.
'broken' is an anagram indicator.
'oar'+'bad'='oarbad'
'oarbad' with letters rearranged gives 'ABOARD'.
(Other definitions for aboard that I've seen before include "A poet penning nothing on vessel" , "Joined for mutual benefit" , "ready to take off" , "On a ship, train, plane or other vehicle" , "On (a ship, train, etc)" .)