The Spanish convict brought over on vessel (7)
I believe the answer is:
galleon
'vessel' is the definition.
(type of ship)
'the spanish convict brought over on' is the wordplay.
'the spanish' becomes 'el' ('the' in Spanish).
'convict' becomes 'lag' (I've seen this before).
'brought over' is a reversal indicator.
'el'+'lag'='ellag'
'ellag' back-to-front is 'galle'.
'galle'+'on'='GALLEON'
(Other definitions for galleon that I've seen before include "Spanish treasure ship" , "Large old square-rigged sailing ship" , "Old Spanish ship" , "Ship of the line" , "Large Spanish sailing ship of yore" .)