Conspirator who made rent bills up (at least three) (5)
I believe the answer is:
casca
'conspirator' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for casca that I've seen before include "Stabbed by him, Caesar" , "envious assassin" , "plotter against Caesar" , "Roman conspirator" , "Conspirator responsible for rent" .)