Crossword Genius

First-class pain caused by treasure (5)

Ross

I believe the answer is:

cache

'treasure' is the definition.
(thesaurus)

'first-class pain' is the wordplay.
'first class' becomes 'c' (ast letter of 'class').
'pain' becomes 'ache' (ache is a kind of pain).
'c'+'ache'='CACHE'

'caused by' acts as a link.

(Other definitions for cache that I've seen before include "Concealed store" , "Secret store, hoard" , "Conceal" , "Nest egg" , "Collection of hidden things" .)

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