Old man under arrest became hysterical (8)
I believe the answer is:
panicked
'hysterical' is the definition.
The answer and definition are not the same part of speech. However, adjectives and past participle verbs occasionally define each other.
'old man under arrest' is the wordplay.
'old man' becomes 'pa' (both can mean someone's father).
'under arrest' becomes 'nicked' (I can't justify this - if you can you should give a lot more credence to this answer).
'pa'+'nicked'='PANICKED'
'became' acts as a link.
Can you help me to learn more?
(Other definitions for panicked that I've seen before include "Scared" , "Became frantic with fear" , "Unnnerved" , "lost nerve" .)