Measure of land, note, in a confined space (7)
I believe the answer is:
acreage
'measure of land' is the definition.
(I've seen this before)
'note in a confined space' is the wordplay.
'note' becomes 're' (**).
'in' is an insertion indicator.
'confined space' becomes 'cage' (I've seen this before).
'a'+'cage'='acage'
're' going inside 'acage' is 'ACREAGE'.
(Other definitions for acreage that I've seen before include "expanse" , "plot" , "Surface area" , "Measure of land" , "Measure used by farmer" .)