Retrograde measure to adopt Latin introduced by Jordan’s capital city (9)
I believe the answer is:
jerusalem
'city' is the definition.
(Jerusalem is an example)
'retrograde measure to adopt latin introduced by jordan's capital' is the wordplay.
'retrograde' says the letters should be written backwards.
'to adopt' means one lot of letters goes inside another.
'latin' becomes 'l'.
'introduced by' is a charade indicator (letters next to each other).
'capital' indicates taking the first letters.
The initial letter of 'jordans' is 'j'.
'measure' enclosing 'l' is 'melasure'.
'melasure' reversed gives 'erusalem'.
'erusalem' put after 'j' is 'JERUSALEM'.
(Other definitions for jerusalem that I've seen before include "Knobbly edible tuber" , "Holy city of Muslims, Jews and Christians" , "Rousing anthem to words by William Blake" , "Zion" , "Holy city in the Middle East" .)