Final, unnegotiable demand will aim to deal with tumult (9)
I believe the answer is:
ultimatum
'final unnegotiable demand will' is the definition.
I can't tell whether this definition defines the answer.
'aim to deal with tumult' is the wordplay.
'to deal with' indicates an anagram (I've seen 'dealt' mean this).
'aim' mixed up with 'tumult' makes 'ULTIMATUM'.
Can you help me to learn more?
(Other definitions for ultimatum that I've seen before include "Uncompromising demand" , "Final point" , "Final statement of actions required of another" , "Final warning" , "Final proposition or demand" .)