Not odd number for service (8)
I believe the answer is:
evensong
'service' is the definition.
(thesaurus)
'not odd number' is the wordplay.
'not odd' becomes 'even' ('even' is the opposite to 'odd').
'number' becomes 'song' (I've seen this before).
'even'+'song'='EVENSONG'
'for' acts as a link.
(Other definitions for evensong that I've seen before include "Service of evening prayer in Church of England" , "Church service late in the day" , "Vespers" , "Late afternoon church service" , "Religious service" .)