Chosen priest principally taking Evensong (5)
I believe the answer is:
elite
'chosen' is the definition.
(I've seen this before)
'priest principally taking evensong' is the wordplay.
'priest' becomes 'eli' (biblical figure).
'principally' suggests taking the first letters.
The first letters of 'taking evensong' is 'te'.
'eli'+'te'='ELITE'
(Other definitions for elite that I've seen before include "Type size; superior group" , "Selected as the best" , "A privileged class of people" , "Group considered to have superior status" , "type in pool?" .)