No-good jetty not as even (7)

I believe the answer is:

bumpier

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'not as even' is the definition.
Although both the answer and definition are comparative adjectives, I can't see how one could define the other.

'no-good jetty' is the wordplay.
'no-good' becomes 'bum' (I've seen this in another clue).
'jetty' becomes 'pier' (I've seen this before).
'bum'+'pier'='BUMPIER'

Can you help me to learn more?

(Other definitions for bumpier that I've seen before include "rougher" , "less smooth" .)

I've seen this clue in The Daily Express.

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