Funny stories in an unsubstantiated statement (9)
I believe the answer is:
assertion
'unsubstantiated statement' is the definition.
'assertion' can be an answer for 'statement' (assertion is a kind of statement). I'm not certain of the 'unsubstantiated' bit.
'funny stories in an' is the wordplay.
'funny' is an anagram indicator.
'in' indicates putting letters inside.
'stories' anagrammed gives 'ssertio'.
'ssertio' put inside 'an' is 'ASSERTION'.
Can you help me to learn more?
(Other definitions for assertion that I've seen before include "Emphatic declaration" , "Claim" , "Confident statement of fact" , "Notarises (anag)" , "Confident declaration" .)