Group from choir turned up (4)
I believe the answer is:
trio
'group' is the definition.
(a group of three)
'from choir turned up' is the wordplay.
'from' indicates the answer is hidden within the clue.
'up' is a reversal indicator (in down clue: letters go upwards).
'oirt' is hidden within 'choir turned'.
'oirt' backwards is 'TRIO'.
(Other definitions for trio that I've seen before include "Bee Gees, Supremes or Andrews Sisters, say" , "Piece for three players" , "Archduke, possibly" , "Three of a kind" , "Musical group" .)