Rate old Boris — and for Macron that's upsetting (5)
I believe the answer is:
tempo
'rate' is the definition.
(tempo is a kind of rate)
'old boris and for macron that's upsetting' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'boris' becomes 'PM' (prime minister Boris Johnson).
'and for macron' becomes 'et' ('and' in French - Emmanuel Macron is French).
'that's upsetting' says the letters should be written in reverse.
'o'+'pm'+'et'='opmet'
'opmet' reversed gives 'TEMPO'.
(Other definitions for tempo that I've seen before include "Beat (music)" , "Pace of a musical piece" , "Time (music)" , "Speed of 3A" , "(Musically) the speed to be played" .)