Large body of salt water (3)
I believe the answer is:
sea
'large body of salt water' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sea that I've seen before include "It's stocked with fish" , "& 14 Ozone" , "E.g Aral or Weddell" , "North for one" , "The briny" .)