In part of church they are on the phone, talking (4)
I believe the answer is:
apse
'in part of church' is the definition.
'apse' can be an answer for 'church' (I've seen this before). I am not certain of the 'in part of' bit.
'they are on the phone talking' is the wordplay.
'they are on the phone' becomes 'apps' (phone applications).
'talking' indicates a 'sounds like' (homophone) clue.
'apps' sounds like 'APSE'.
Can you help me to learn more?
(Other definitions for apse that I've seen before include "Architectural feature in a church" , "Semicircular end of a church, behind the altar" , "Where the altar is usually found in a church" , "Recess at eastern end of a church" , "place in church" .)