Sad ending? (4)
I believe the answer is:
ness
'sad ending?' 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 lake with traditional monster" , "something added for quality" , "Scottish Loch famed for monster" , "Headland, cape" , "Scottish Lough containing legendary monster" .)