Choppy sea, ultimately stormy, not a problem (4)
I believe the answer is:
easy
'not a problem' is the definition.
(I've seen this in another clue)
'choppy sea ultimately stormy' is the wordplay.
'choppy' is an anagram indicator.
'ultimately' suggests the final letters.
The last letter of 'stormy' is 'y'.
'sea' anagrammed gives 'eas'.
'eas'+'y'='EASY'
(Other definitions for easy that I've seen before include "Effortless, uncomplicated" , "careful!" , "Obliging; go carefully" , "Posing no difficulty" , "Undemanding" .)