Cabinet minister drives payroll reforms (4,5,4)
I believe the answer is:
lord privy seal
'cabinet minister' is the definition.
(Lord Privy Seal is an example)
'drives payroll reforms' is the wordplay.
'reforms' indicates an anagram.
'drives'+'payroll'='drivespayroll'
'drivespayroll' anagrammed gives 'LORD PRIVY SEAL'.
(Other definitions for lord privy seal that I've seen before include "Top cabinet minister" , "minister's office" , "Cabinet member" , "Senior cabinet minister" , "high official" .)