Panic as hairstyle has length cut off (8)
I believe the answer is:
hysteria
'panic' is the definition.
(hysteria is uncontrollable panic)
I don't understand how the rest of the clue works.
(Other definitions for hysteria that I've seen before include "Extreme emotional state of instability" , "craze" , "Wild emotionalism" , "Panic" , "Psychoneurotic condition" .)