Quick to change fibre (5)
I believe the answer is:
brief
'quick' is the definition.
(thesaurus)
'change fibre' is the wordplay.
'change' indicates anagramming the letters.
'fibre' is an anagram of 'BRIEF'.
'to' acts as a link.
(Other definitions for brief that I've seen before include "Case given to a barrister" , "Fibre (anag.)" , "Solicitor" , "Terse" , "Summary of facts for barrister to consider" .)