Crossword Genius

Paddler used ocean first (8)

Ross

I believe the answer is:

canoeist

'paddler' is the definition.
(synonyms)

'used ocean first' is the wordplay.
'used' indicates anagramming the letters.
'first' becomes 'ist' (ist resembles 1st).
'ocean' with letters rearranged gives 'canoe'.
'canoe'+'ist'='CANOEIST'

(Other definitions for canoeist that I've seen before include "sportsman" , "Paddler" , "One using light boat" , "rower" , "Person who paddles a kayak or suchlike" .)

I've seen this clue in The Daily Express.
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