A tyrant emerges the first day riot act is reformed (8)
I believe the answer is:
dictator
'a tyrant' is the definition.
(I've seen this before)
'day riot act is reformed' is the wordplay.
'day' becomes 'd' (abbreviation for day).
'is reformed' is an anagram indicator.
'riot'+'act'='riotact'
'riotact' with letters rearranged gives 'ictator'.
'd'+'ictator'='DICTATOR'
'emerges the first' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for dictator that I've seen before include "Despot" , "person in charge? Absolutely!" , "One ordering" , "Tyrant or oppressor" , "Stalin was one, and Mussolini" .)