A credit expert's beginning to get the measure of land (4)
'the measure of land' is the definition.
(I've seen this before)
'a credit expert's beginning to' is the wordplay.
'credit' becomes 'cr'.
'beginning to' indicates taking the first letters.
The first letter of 'experts' is 'e'.
'get' acts as a link.
(Other definitions for acre that I've seen before include "Area measure - Israeli port - Brazilian state", "Mediterranean port", "4840 sq yds", "Ancient city in Israel", "Unit of land area".)