Full of ups and downs, naturally (5)

I believe the answer is:

hilly

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'full of ups and downs' is the definition.
(I've seen this in another clue)

I don't understand how the rest of the clue works.

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(Other definitions for hilly that I've seen before include "Descriptive of undulating upland" , "Like Chiltern or Cotswolds areas" , "Mountainous" , "Not flat (country)" , "(Of a landscape) not flat" .)

I've seen this clue in the Evening Standard.

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