Legendary loch (4)
I believe the answer is:
ness
'legendary loch' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ness that I've seen before include "Scottish Lough containing legendary monster" , "Loch of monster fame" , "head" , "Loch in the Great Glen" , "Headland, cape" .)