Maintaining an area of land (7)
I believe the answer is:
holding
'maintaining' is the definition.
('hold' can be a synonym of 'maintain')
'an area of land' is the wordplay.
'an area' becomes 'hold' (hold is a kind of area).
'of land' becomes 'ing' (I can't justify this - if you can you should give a lot more credence to this answer).
'hold'+'ing'='HOLDING'
Can you help me to learn more?
(Other definitions for holding that I've seen before include "In possession of" , "-- Company; -- pattern" , "Grasping" , "Keeping within grasp" , "Farm; stacking (of aircraft waiting to land)" .)