Hear ditty ultimately hummable? (6)
I believe the answer is:
catchy
'hummable?' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for catchy that I've seen before include "Tuneful and easily remembered" , "like certain tunes?" , "Of tune, lilting and easy to remember" , "like memorable tunes" , "Of a tune, lively and easy to remember" .)