Onassis, say, would now perish at sea (9)
I believe the answer is:
shipowner
'onassis say would' is the definition.
I can't tell whether this definition defines the answer.
'now perish at sea' is the wordplay.
'at sea' indicates an anagram.
'now'+'perish'='nowperish'
'nowperish' with letters rearranged gives 'SHIPOWNER'.
Can you help me to learn more?
(Other definitions for shipowner that I've seen before include "Onassis, say" , "I've secured brig" , "Crafty proprietor" , "man over the line" .)