Mechanic making a terrific mess (9)
I believe the answer is:
artificer
'mechanic' is the definition.
(thesaurus)
'a terrific mess' is the wordplay.
'mess' indicates anagramming the letters.
'terrific' is an anagram of 'rtificer'.
'a'+'rtificer'='ARTIFICER'
'making' is the link.
(Other definitions for artificer that I've seen before include "Skilled craftsman" , "One into skill" , "Mechanic in the armed forces" , "Skilled worker" , "Military mechanic" .)