Excited Celt describing a conspicuous success (5)
I believe the answer is:
eclat
'conspicuous success' is the definition.
(eclat means an impressive level of success)
'excited celt describing a' is the wordplay.
'excited' indicates an anagram.
'describing' indicates putting letters inside (describe can mean to form the outline of).
'celt' with letters rearranged gives 'eclt'.
'eclt' enclosing 'a' is 'ECLAT'.
(Other definitions for eclat that I've seen before include "Universal approval" , "French renown" , "French social distinction or success" , "Brilliant success - striking effect" , "Loud applause" .)