One who won't allow this kind of headline (6)
I believe the answer is:
banner
'headline' is the definition.
(I've seen this in another clue)
'one who won't allow this kind' is the wordplay.
I cannot really see how this works, but
'one' could be 'er' (I've seen this in other clues) and 'er' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for banner that I've seen before include "Flag used as standard" , "Flag with a slogan" , "One not allowing" , "It may be seen on demo" , "Flag; headline" .)