Pets playing with alien group (6)
I believe the answer is:
septet
'group' is the definition.
The answer is an example.
'pets playing with alien' is the wordplay.
'playing' indicates an anagram.
'with' is a charade indicator (letters next to each other).
'alien' becomes 'et' (extra terrestrial).
'pets' is an anagram of 'sept'.
'sept'+'et'='SEPTET'
(Other definitions for septet that I've seen before include "Musical group" , "Group of seven performers or singers" , "piece by Beethoven" , "A group of seven, say singers" , "Work for seven players" .)