Five peers organised second service (7)
I believe the answer is:
vespers
'service' is the definition.
(vespers is a church service)
'five peers organised second' is the wordplay.
'five' becomes 'V' (Roman numeral).
'organised' indicates an anagram.
'second' becomes 's' (common abbreviation).
'peers' anagrammed gives 'esper'.
'v'+'esper'+'s'='VESPERS'
(Other definitions for vespers that I've seen before include "Evening prayers" , "Evening service" , "An hour of worship" , "Evensong - RC service" .)