Gather with capacity to contain returning chaos (8)
I believe the answer is:
assemble
'gather' is the definition.
(I know that gather can be written as assemble)
'with capacity to contain returning chaos' is the wordplay.
'with capacity' becomes 'able'.
'to contain' means one lot of letters goes inside another.
'returning' shows that the letters should be reversed in order.
'chaos' becomes 'mess' (I've seen this before).
'mess' written backwards gives 'ssem'.
'able' going around 'ssem' is 'ASSEMBLE'.
(Other definitions for assemble that I've seen before include "Put together all the components" , "Gather or collect together" , "Bring/come together" , "Build" , "Come or bring group together" .)