Ship with pirate (7)
I believe the answer is:
brigand
'pirate' is the definition.
(brigand is a type of thief)
'ship with' is the wordplay.
'ship' becomes 'brig' (I've seen this before).
'with' becomes 'and'.
'brig'+'and'='BRIGAND'
(Other definitions for brigand that I've seen before include "Country robber" , "Marauder" , "Gang member" , "Pirate" , "Highway robber" .)