Group with skill covering chaos up (8)
I believe the answer is:
assembly
'group' is the definition.
(assembly is a kind of group)
'with skill covering chaos up' is the wordplay.
'with skill' becomes 'ably' (I've seen this before).
'covering' means one lot of letters goes inside another.
'chaos' becomes 'mess' (I've seen this before).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'mess' back-to-front is 'ssem'.
'ably' placed around 'ssem' is 'ASSEMBLY'.
(Other definitions for assembly that I've seen before include "This line is a sequence of machines and workers" , "Gathering, congregation" , "Gathering of people or fitting of parts together" , "Bless May (anag.)" , "Body of people that meets" .)