The bursar is more certain to follow exchange rate (9)
I believe the answer is:
treasurer
'the bursar' is the definition.
(thesaurus)
'more certain to follow exchange rate' is the wordplay.
'more certain' becomes 'surer' ('sure' can be a synonym of 'certain').
'to follow' says to put letters next to each other.
'exchange' is an anagram indicator.
'rate' with letters rearranged gives 'trea'.
'surer' after 'trea' is 'TREASURER'.
'is' is the link.
(Other definitions for treasurer that I've seen before include "Official in charge of finances" , "Financial officer" , "He handles the money for an organisation" , "Committee member" , "Club official" .)