Main network found in roof space (8)
I believe the answer is:
atlantic
'main' is the definition.
(Atlantic is an example)
'network found in roof space' is the wordplay.
'network' becomes 'LAN' (Local Area Network).
'found in' indicates putting letters inside.
'roof space' becomes 'attic' (I've seen this before).
'lan' going within 'attic' is 'ATLANTIC'.
(Other definitions for atlantic that I've seen before include "Azores, Falklands, in it" , "main" , "Second-largest ocean" , "deep water" , "One of earth's oceans" .)