Crossword Genius

Disturbing conundrum ultimately leaves cabinet chasing its tail (8)

Ross

I believe the answer is:

sinister

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

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

'conundrum ultimately leaves cabinet chasing its tail' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'its' is 'ist' which is present in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for sinister that I've seen before include "Disturbing" , ", nun going round home" , "Threatening the left in heraldry" , "Forbidding" , "'Ominous, baleful (8)'" .)

I've seen this clue in The Independent.
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