Crossword Genius

However stock rotates, one's behind (8)

Ross

I believe the answer is:

buttocks

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

'behind' is the definition.
(synonyms)

'however stock rotates one's' is the wordplay.
I cannot quite understand how this works, but
'however' could be 'but' (I've seen this before) and 'but' is found within the answer.
an anagram of 'stock' is 'tocks' which is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for buttocks that I've seen before include "Get behind" , "Bottom" , "Sit on them" , "Body parts covered at least by 13" , "Rear" .)

I've seen this clue in The Independent.
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