Loch ____ (4)
I believe the answer is:
ness
'loch' is the definition.
(Loch Ness in Scotland)
This is all the clue.
(Other definitions for ness that I've seen before include "Loch of monster fame" , "Scottish Loch with legendary monster" , "Scottish Loch famed for monster" , "Eliot -, led effort against Al Capone; Scots loch" , "Headland, promontory" .)