Stormy sea for this person is terrifying (8)
I believe the answer is:
fearsome
'is terrifying' is the definition.
(I've seen this before)
'stormy sea for this person' is the wordplay.
'stormy' is an anagram indicator.
'this person' becomes 'me' (I've seen this in other clues).
'sea'+'for'='seafor'
'seafor' is an anagram of 'fearso'.
'fearso'+'me'='FEARSOME'
(Other definitions for fearsome that I've seen before include "Formidable" , "Frightening, terrible" , "Dreadful" , "Frightful" , "Daunting" .)