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