Crossword Genius

Study agreements head of state promoted (8)

Ross

I believe the answer is:

treatise

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

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(Other definitions for treatise that I've seen before include "Academic composition" , "Formal written work dealing with a particular subject" , "Tract, monograph" , "Formal exposition" , "Iterates in dissertation" .)

I've seen this clue in The Times.
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