Spout about how you waive all rights to? (7)

I believe the answer is:

declaim

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'spout' is the definition.
(I know that spout can be written as declaim)

I can't explain the remainder of the clue.

(Other definitions for declaim that I've seen before include "Speak dramatically" , "Deliver (words) rhetorically" , "Medical (anag)" , "attack" , "Deliver an impassioned speech" .)

I've seen this clue in the Evening Standard.

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