Unprincipled company abolished after I break in (6)

I believe the answer is:

irrupt

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

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

I cannot understand how the remainder of the clue works.

(Other definitions for irrupt that I've seen before include "Enter forcibly and suddenly" , "Break, rush, in" , "Enter forcibly or violently" .)

I've seen this clue in The Independent.

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