It's up to old European statesman (4)
I believe the answer is:
tito
'old european statesman' is the definition.
(Josip Broz Tito, former Yugoslav president)
'it's up to' is the wordplay.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'it' backwards is 'ti'.
'ti'+'to'='TITO'
(Other definitions for tito that I've seen before include "Josip Broz pseudonym" , "Statesman once" , "Adopted name of Josip Broz, Yugoslav leader" , "Head of state" , "Josip Broz, d. 1980" .)