Plain southern woman digesting version of Bible (7)
I believe the answer is:
savanna
'plain' is the definition.
(a savanna is a grassy plain)
'southern woman digesting version of bible' is the wordplay.
'southern' becomes 's' (abbreviation).
'woman' becomes 'anna' ().
'digesting' indicates putting letters inside (inserted letters are eaten or ingested).
'version of bible' becomes 'AV' (abbreviation for Authorised Version).
's'+'anna'='sanna'
'sanna' placed around 'av' is 'SAVANNA'.
(Other definitions for savanna that I've seen before include "Large grassy plain with few trees" , "Flat, tropical grassland" , "Open grasslands of Africa" , "Grassy (African) plain" , "Tropical African grasslands" .)