Ship aims to leave international harbour (9)
I believe the answer is:
transport
'ship' is the definition.
(transport ship is a kind of ship)
'aims to leave international harbour' is the wordplay.
'aims' becomes 'trains' (as in training a gun on something).
'to leave' is a deletion indicator.
'international' becomes 'i' (abbreviation eg in IMF).
'harbour' becomes 'port' (I've seen this before).
'trains' with 'i' removed is 'trans'.
'trans'+'port'='TRANSPORT'
(Other definitions for transport that I've seen before include "Take from one place to another" , "Carry and throw into ecstasy." , "Move (from place to place)" , "trap, for example" , "bus maybe?" .)