Rich spent wildly to acquire muscle (9)

I believe the answer is:

sphincter

'muscle' is the definition.
(I know that sphincter is a type of muscle)

'rich spent wildly' is the wordplay.
'wildly' indicates anagramming the letters.
'rich'+'spent'='richspent'
'richspent' is an anagram of 'SPHINCTER'.

'to acquire' acts as a link.

I've seen this clue in The Guardian.

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