Lowland area (4)
I believe the answer is:
vale
'lowland area' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for vale that I've seen before include "Cheers" , "Maida -, N. London area; farewell (archaic)" , "Valley" , "Trough between ridges" , "Glen; goodbye!" .)