One might rile the Simpson boy, making him cranky (9)
I believe the answer is:
irritable
'cranky' is the definition.
(I know that cranky can be written as irritable)
'one might rile the simpson boy making him' is the wordplay.
I cannot really see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
'boy' could be 'ab' and 'ab' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for irritable that I've seen before include "Easily annoyed" , "Fractious" , "Peevish" , "snappy" , "Cantankerous" .)