Low spirits of a cavity (10)

I believe the answer is:

depression

I believe this clue is a double definition.

'low spirits' is the first definition.
(thesaurus)

'a cavity' is the second definition.
(thesaurus)

'of' acts as a link.

(Other definitions for depression that I've seen before include "Pit" , "Nineteen twenty nine financial slump" , "valley" , "Bad times" , "mental anguish" .)

I've seen this clue in the Sydney Morning Herald.

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