Odd verses, beginning of prayer included, in evensong (7)
I believe the answer is:
vespers
'evensong' is the definition.
('vespers' can be a synonym of 'evensong')
'odd verses beginning of prayer included' is the wordplay.
'odd' indicates an anagram.
'beginning of' says to take the initial letters.
'included' is an insertion indicator.
The first letter of 'prayer' is 'p'.
'verses' with letters rearranged gives 'vesers'.
'vesers' enclosing 'p' is 'VESPERS'.
'in' acts as a link.
(Other definitions for vespers that I've seen before include "An hour of worship" , "Evensong - RC service" , "Evening prayers" , "Evening service" .)