Grow up! Not right head of state is sounding off … (6)

I believe the answer is:

spouts

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But I can't explain it at all! Could you help me understand?

(Other definitions for spouts that I've seen before include "Declaims; jets" , "Pontificates - toss-up (anag)" , "Openings for passage of liquids" , "Gushes" , "Sends out as liquid jets" .)

I've seen this clue in The Guardian.

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