Son argued jittery characters could become treacherous (9)
I believe the answer is:
dangerous
'treacherous' is the definition.
(similar in meaning)
'son argued jittery' is the wordplay.
'jittery' indicates anagramming the letters.
'son'+'argued'='sonargued'
'sonargued' with letters rearranged gives 'DANGEROUS'.
'characters could become' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for dangerous that I've seen before include "likely to blow up" , "posing risk" , "Perilous, unsafe" , "Not safe" , "Harmful, injurious" .)