Wavy dippy seas troubled tummy (9)

I believe the answer is:

dyspepsia

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'troubled tummy' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'wavy dippy seas' is the wordplay.
'wavy' indicates anagramming the letters (letters wave around).
'dippy'+'seas'='dippyseas'
'dippyseas' is an anagram of 'DYSPEPSIA'.

Can you help me to learn more?

(Other definitions for dyspepsia that I've seen before include "Stomach upset - spied a spy (anag)" , "Heartburn" , "digestive problem" , "Indigestion" , "stomach complaint" .)

I've seen this clue in The Independent.

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