Large stream (5)
I believe the answer is:
river
'large stream' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for river that I've seen before include "Eg, Severn" , "Slow-cooked meat dish" , "Eg, Thames or Nile" , "Eg, Trent" , "Moon - - (song)" .)