Huge current stopping at sea intact (7)
I believe the answer is:
titanic
'huge' is the definition.
(thesaurus)
'current stopping at sea intact' is the wordplay.
'current' becomes 'i' (symbol for electric current).
'stopping' is an insertion indicator (stopping can mean blocking a gap).
'at sea' is an anagram indicator.
'intact' is an anagram of 'titanc'.
'i' placed inside 'titanc' is 'TITANIC'.
(Other definitions for titanic that I've seen before include "Of great force or power, like the ill-fated ship" , "In attic (anag.)" , "Ill-fated vessel" , "Famous doomed transatlantic liner" , "Hugely strong (but lost!)" .)