Group starting our choir thanked everyone there that evening (7)
I believe the answer is:
octette
'group' is the definition.
The answer is an example.
'starting our choir thanked everyone there that evening' is the wordplay.
'starting' says to take the initial letters.
The first letters of 'our choir thanked everyone there that evening' is 'OCTETTE'.
(Other definitions for octette that I've seen before include "Group of eight" , "Noted work" , "Eight musicians" .)