Ridiculous, ridiculous, ridiculous. I quit! (9)
I believe the answer is:
ludicrous
'ridiculous' is the definition.
(I know that ridiculous can be written as ludicrous)
'ridiculous ridiculous i quit' is the wordplay.
'ridiculous' indicates an anagram.
'quit' suggests deleting specific letters.
'ridiculous' with 'i' removed is 'rdiculous'.
'rdiculous' anagrammed gives 'LUDICROUS'.
(Other definitions for ludicrous that I've seen before include "Farcical" , "Silly and laughable" , "Ridiculously foolish" , "Absurd, ridiculous" , "Utterly laughable" .)