Curious, Guardian's questionable statement (6)
I believe the answer is:
'questionable statement' is the definition.
(a rumour may be questionable or unreliable)
'curious guardian's' is the wordplay.
'curious' becomes 'rum' (synonyms).
'guardian's' becomes 'our' (belonging to the newspaper the puzzle is part of).
(Other definitions for rumour that I've seen before include "Story going around" , "buzz" , "What "a little bird" tells you?" , "Doubtful story" , "Unverified report" .)