Spacious, extensive (4)
I believe the answer is:
wide
This clue is a double definition.
'spacious' is the first definition.
(I've seen this before)
'extensive' is the second definition.
(similar in meaning)
(Other definitions for wide that I've seen before include "Far from the mark" , "roomy" , "lax in morals" , "Unplayable ball (cricket)" , "Spacious; an extra" .)