Too unfunny hiding something up one's sleeve — I don't want it! (2,5,3)
I believe the answer is:
no thank you
Here is my best explanation:
'i don't want it' is the definition.
'too unfunny hiding something up one's sleeve' is the subsidiary indication.
I cannot quite understand how this works, but
'one' could be 'an' (I've seen this in other clues) and 'an' is present in the answer.
This explanation may well be incorrect...