Titanic sinker (7)
I believe the answer is:
iceberg
'titanic sinker' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for iceberg that I've seen before include "Frozen shipping hazard" , "Large mass of floating ice" , "Hazard of polar seas" , "shunned by sailors?" , "calf, perhaps" .)