I am dust, having decayed in the ground (7)

I believe the answer is:

stadium

I'm a little stuck... Click here to teach me more about this clue!

'the ground' is the definition.
(I've seen this before)

'i am dust having decayed' is the wordplay.
'i am dust' can be anagrammed to 'STADIUM'.
Though, I'm not sure how this is indicated.

'in' acts as a link.

Can you help me to learn more?

(Other definitions for stadium that I've seen before include "Open-air sports venue" , "Venue for sporting events, concerts etc" , "Sports arena" , "Admit us (anag) - sports ground" , "bowl?" .)

I've seen this clue in The Guardian.

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