Bush changed history in foreign affairs, primarily (9)
I believe the answer is:
forsythia
'bush' is the definition.
(forsythia is a kind of bush)
'changed history in foreign affairs primarily' is the wordplay.
'changed' indicates an anagram.
'in' indicates putting letters inside.
'primarily' says to take the initial letters.
The first letters of 'foreign affairs' is 'fa'.
'history' anagrammed gives 'orsythi'.
'orsythi' inserted within 'fa' is 'FORSYTHIA'.
(Other definitions for forsythia that I've seen before include "A frosty hi to the flowering shrub" , "Bush" , "bloomer in spring" , "Ornamental shrub" , "Floral shrub" .)