Chaotic when a new chief's in charge (8)
I believe the answer is:
anarchic
'chaotic' is the definition.
(thesaurus)
'a new chief's in charge' is the wordplay.
'a new' becomes 'an' (I've seen this in other clues).
'chief' becomes 'arch' ('arch' can be a synonym of 'chief').
'in charge' becomes 'ic'.
'an'+'arch'+'ic'='ANARCHIC'
'when' acts as a link.
(Other definitions for anarchic that I've seen before include "Anti-government" , "Totally without rules" , "Lawless, out of control behaviour" , "Disorderly" , "Car chain (anag.)" .)