Have time away from built-up area (3)
I believe the answer is:
own
'have' is the definition.
('own' can be a synonym of 'have')
'time away from built-up area' is the wordplay.
'time' becomes 't'.
'away from' indicates named letters should be taken away.
'built up area' becomes 'town' (I've seen this before).
'town' with 't' removed is 'OWN'.
(Other definitions for own that I've seen before include "Posses" , "Private" , "Keep" , "Acknowledge" , "Possess or confess" .)