Anger that smoulders in church service (7)
I believe the answer is:
incense
'anger that smoulders' is the definition.
'incense' can be an answer for 'anger' (to incense is make angry). I am not certain of the rest of the definition.
'in church service' is the wordplay.
'church service' becomes 'cense' (I can't justify this - if you can you should believe this answer much more).
'in'+'cense'='INCENSE'
Can you help me to learn more?
(Other definitions for incense that I've seen before include "To outrage" , "A High Church feature" , "Rouse to anger" , "can cause strong emotion" , "Enrage - fragrant material for burning" .)