Alarming felony? (5)
I believe the answer is:
arson
'alarming felony?' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for arson that I've seen before include "Crime of fire setting" , "Pyromaniac's crime" , "Incendiary crime" , "Incendiarism" , "Fire-raiser's crime" .)