Extensive area of land (5)
I believe the answer is:
tract
'extensive area of land' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for tract that I've seen before include "religious work in > area" , "Pamphlet, large expanse of land" , "lot of ground?" , "Large area; treatise" , "religious work, often" .)