Denies there's no fifth puzzle (5)
I believe the answer is:
rebus
'puzzle' is the definition.
(type of visual puzzle)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for rebus that I've seen before include "solver?" , "Pictorial wordplay" , "Picture-letter puzzle" , "that's puzzling" , "Enigmatic representation" .)