Sailor in violent rain in French sea (7)
I believe the answer is:
mariner
'sailor' is the definition.
(mariner is a kind of sailor)
'violent rain in french sea' is the wordplay.
'violent' indicates an anagram.
'in' means one lot of letters goes inside another.
'french sea' becomes 'mer' ('sea' in French).
'rain' with letters rearranged gives 'arin'.
'arin' inserted into 'mer' is 'MARINER'.
'in' is the link.
(Other definitions for mariner that I've seen before include "Seafarer, old salt" , "Jack" , "Sea dog" , "Man of the sea" , "Sailor" .)