Sound of phone ultimately jarring during start of religious chant (8)
I believe the answer is:
ringtone
'sound of phone' is the definition.
'ringtone' can be an answer for 'sound' (I have seen 'Mobile sound ' mean 'ringtone' so perhaps 'sound' could also mean 'ringtone'). I'm not sure about the 'of phone' bit.
'ultimately jarring during start of religious chant' is the wordplay.
'ultimately' says to take the final letters.
'during' indicates putting letters inside.
'start of' suggests taking the first letters.
'chant' becomes 'intone' (synonyms).
The final letter of 'jarring' is 'g'.
The initial letter of 'religious' is 'r'.
'r'+'intone'='rintone'
'g' going into 'rintone' is 'RINGTONE'.
Can you help me to learn more?
(Other definitions for ringtone that I've seen before include "Sound heard when someone telephones" , "Sound coming from mobile" , "Sound of modern life" , "Nitrogen (anag.)" , "Sound made by a mobile phone" .)