___ Amendment (2010s extension of the Kyoto Protocol) (4)
(Other definitions for doha that I've seen before include "Capital of Qatar" , "Gulf resort" , "Trade round" .)
'amendment' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for reform that I've seen before include "Correct(ion of) abuses" , "Mend one's ways" , "Change one's ways (for the better?)" , "Show improvement" , "Abandon evil practices" .)