He owns a fair bit in the outskirts of Loch Lomond (5)
I believe the answer is:
laird
'he owns a fair' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'bit in the outskirts of loch lomond' is the wordplay.
'bit' becomes 'i' (resembles l, a binary digit or bit).
'in the' means one lot of letters goes inside another.
'outskirts of loch lomond' becomes 'lard' (I can't explain this - if you can you should give a lot more credence to this answer).
'i' put into 'lard' is 'LAIRD'.
Can you help me to learn more?
(Other definitions for laird that I've seen before include "Scots estate owner" , "Big landowner" , "He's landed in Scotland" , "Scottish estate-owner" , "Scottish landowner" .)