Still stormy, neither vessel leaves Italy (12)
I believe the answer is:
nevertheless
'still' is the definition.
(synonyms)
'stormy neither vessel leaves italy' is the wordplay.
'stormy' indicates an anagram.
'leaves' indicates named letters should be taken away.
'italy' becomes 'i'.
'neither'+'vessel'='neithervessel'
'neithervessel' with 'i' taken out is 'nethervessel'.
'nethervessel' anagrammed gives 'NEVERTHELESS'.
(Other definitions for nevertheless that I've seen before include "However" , "Notwithstanding" , "at any rate" , "But always" , "In spite of everything" .)