Large groups horsed around (6)
I believe the answer is:
hordes
'large groups' is the definition.
(I've seen this in another clue)
'horsed around' is the wordplay.
'around' indicates an anagram.
'horsed' is an anagram of 'HORDES'.
(Other definitions for hordes that I've seen before include "Bands" , "large numbers" , "Horsed around with the multitudes" , "Huge noisy crowds" , "Vast multitudes" .)