Expanse of land with nice sylvan area originally included — do business (8)
I believe the answer is:
transact
'do business' is the definition.
(I've seen this before)
'expanse of land with nice sylvan area originally included' is the wordplay.
'expanse of land' becomes 'tract'.
'with' means one lot of letters goes inside another.
'nice' becomes 'n' (this could be a standard abbreviation which I don't know about).
'originally' indicates taking the first letters.
'included' means one lot of letters goes inside another.
The initial letters of 'sylvan area' is 'sa'.
'tract' placed around 'n' is 'tranct'.
'tranct' enclosing 'sa' is 'TRANSACT'.
(Other definitions for transact that I've seen before include "Manage" , "Conduct business, negotiate" , "Deal with" , "Buy or sell" , "Carry out, like business" .)