A lot of land gives power re the number of years (7)
I believe the answer is:
acreage
'a lot of land' is the definition.
I can't tell whether this defines the answer.
'power re the number of years' is the wordplay.
'power' becomes 'AC' (AC is an example).
'the number of years' becomes 'age'.
'ac'+'re'+'age'='ACREAGE'
'gives' is the link.
Can you help me to learn more?
(Other definitions for acreage that I've seen before include "Extent of ground" , "plot" , "Measure of land" , "Area measure" , "expanse" .)