Riot distressed group (4)
I believe the answer is:
trio
'group' is the definition.
(a group of three)
'riot distressed' is the wordplay.
'distressed' indicates anagramming the letters.
'riot' anagrammed gives 'TRIO'.
(Other definitions for trio that I've seen before include "Bee Gees, Supremes or Andrews Sisters, say" , "A group or set of three" , "Three together" , "Work for three" , "Piece for three players" .)