Live on a field (4)
I believe the answer is:
area
'field' is the definition.
(synonyms)
'live on a' is the wordplay.
'live' becomes 'are' (both can mean exist).
'on' is a charade indicator (letters next to each other).
'are'+'a'='AREA'
(Other definitions for area that I've seen before include "part of town" , "Extent of a two-dimensional surface" , "topic" , "Speaking formally to (someone)" , "Patch" .)