Unit AMM, in chaos, is set free (7)
I believe the answer is:
manumit
'set free' is the definition.
(manumitting is a kind of setting free)
'unit amm in chaos' is the wordplay.
'in chaos' is an anagram indicator.
'unit'+'amm'='unitamm'
'unitamm' is an anagram of 'MANUMIT'.
'is' is the link.
(Other definitions for manumit that I've seen before include "deliver" , "release" , "Set free from slavery - anti-mum (anag)" .)