Short guy in purple up before a tyrant (8)
I believe the answer is:
caligula
'up before a tyrant' is the definition.
I can't judge whether this definition defines the answer.
'short guy in purple' is the wordplay.
'short' means to remove the last letter.
'guy' becomes 'cat' (American slang for man, esp in Jazz).
'in purple' becomes 'ligula' (I am not sure about this - if you are sure you should believe this answer much more).
'cat' with its last letter taken away is 'ca'.
'ca'+'ligula'='CALIGULA'
Can you help me to learn more?
(Other definitions for caligula that I've seen before include "Successor to Tiberius" , "Emperor after Tiberius" , "The Roman emperor said to have made his horse a consul" , "Roman emperor, notorious for his cruelty" , "imperial figure" .)