Short fibre in a tangle (5)
I believe the answer is:
brief
'short' is the definition.
(synonyms)
'fibre in a tangle' is the wordplay.
'in a tangle' indicates an anagram.
'fibre' is an anagram of 'BRIEF'.
(Other definitions for brief that I've seen before include "Ephemeral" , "Fibre (anag.)" , "Short - work for counsel" , "Short - work for a barrister" , "Provide someone with the facts of the case" .)