Tiresome types speak so in due course (2,6)

I believe the answer is:

at length

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

I can't explain the remainder of the clue.

(Other definitions for at length that I've seen before include "eventually" , "For an extended period" , "In full detail" , "In detail, taking a long time" , "Fully extended" .)

I've seen this clue in The Sun.

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