Live action’s beginning in region (4)
I believe the answer is:
area
'region' is the definition.
('area' can be a synonym of 'region')
'live action's beginning' is the wordplay.
'live' becomes 'are' (both can mean exist).
'beginning' says to take the initial letters.
The first letter of 'action' is 'a'.
'are'+'a'='AREA'
'in' is the link.
(Other definitions for area that I've seen before include "Region, zone" , "Patch" , "Territory" , "Region, space" , "part of town" .)