Article in comic is only a rumour (6)
I believe the answer is:
canard
'only a rumour' is the definition.
'article in comic' is the wordplay.
'article' becomes 'an' (indefinite article).
'in' indicates putting letters inside.
'comic' becomes 'card' (old-fashioned term for a humorous person).
'an' placed inside 'card' is 'CANARD'.
'is' is the link.
(Other definitions for canard that I've seen before include "Baseless rumour" , "False rumour or story, from France" , "Ugly rumour" , "A French kind of false rumour" , "'False report, hoax (6)'" .)