Peas mashed in church area (4)
I believe the answer is:
apse
'church area' is the definition.
(I've seen this in another clue)
'peas mashed' is the wordplay.
'mashed' indicates anagramming the letters.
'peas' anagrammed gives 'APSE'.
'in' acts as a link.
(Other definitions for apse that I've seen before include "Semicircular recess in church" , "Recess with domed rof in a church" , "Recess at eastern end of a church" , "Offshoot from the choir, nave or aisle in a church" , "may be seen in church!" .)