New vessel there at sea, in spite of everything (12)
I believe the answer is:
nevertheless
'in spite of everything' is the definition.
(I've seen this before)
'new vessel there at sea' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'at sea' indicates an anagram.
'vessel'+'there'='vesselthere'
'vesselthere' is an anagram of 'evertheless'.
'n'+'evertheless'='NEVERTHELESS'
(Other definitions for nevertheless that I've seen before include "However" , "But always" , "anyhow" , "Still" , "In spite of everything" .)