Oceanic shocker (7)
I believe the answer is:
torpedo
'oceanic shocker' is the definition.
(type of fish which might give an electric shock)
This is the entire clue.
(Other definitions for torpedo that I've seen before include "Explosive missile from submarine" , "American sandwich made with a long split roll" , "Sea-borne missile" , "(Of a project) cause to sink without trace" , "Sub's missile" .)