On choppy seas, English surfer finally wipes out (6)
I believe the answer is:
erases
'wipes out' is the definition.
('erase' can be a synonym of 'wipe out')
'on choppy seas english surfer finally' is the wordplay.
'on' means one lot of letters go next to another.
'choppy' indicates anagramming the letters.
'english' becomes 'e' (abbreviation).
'finally' says to take the final letters.
The last letter of 'surfer' is 'r'.
'seas' anagrammed gives 'ases'.
'e'+'r'='er'
'ases' put after 'er' is 'ERASES'.
(Other definitions for erases that I've seen before include "Removes all traces" , "Obliterates" , "Rubs out, deletes" .)