Resolve to change US president (9)
I believe the answer is:
roosevelt
'us president' is the definition.
(I've seen this before)
'resolve to change' is the wordplay.
'change' is an anagram indicator.
'resolve'+'to'='resolveto'
'resolveto' anagrammed gives 'ROOSEVELT'.
(Other definitions for roosevelt that I've seen before include "32nd US president, Franklin" , "Teddy" , "Surname of 26th and 32nd US presidents" , "former president" , "See president" .)