Mad son to be released? That's pointless (5)
I believe the answer is:
inane
'that's pointless' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for inane that I've seen before include "Thick" , "Dull-witted" , "Silly or senseless" , "Fatuous, asinine" , "Silly, fatuous" .)