Quiet about group’s reluctance to work (5)
I believe the answer is:
sloth
'reluctance to work' is the definition.
(sloth is laziness)
'quiet about group's' is the wordplay.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'about' means one lot of letters goes inside another.
'group' becomes 'lot'.
'sh' going around 'lot' is 'SLOTH'.
(Other definitions for sloth that I've seen before include "One's often suspended from tree" , "Idleness" , "Idle creature" , "Sluggish creature" , "one of a deadly group" .)