Intrude by chance or accident (8)

I believe the answer is:

encroach

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

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

'chance or accident' is the wordplay.
'chance or' can be anagrammed to 'ENCROACH'.
But, I'm unsure how the anagram is indicated.

'by' is the link.

Can you help me to learn more?

(Other definitions for encroach that I've seen before include "Intrude on somebody's territory or time" , "Intrude on another's property or rights" , "Enter upon another's property or rights" , "Make inroads" , "Intrude on someone's territory or time" .)

I've seen this clue in The Telegraph, The Globe and Mail and The Guardian.

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