Brevity so different to loquacity (9)
I believe the answer is:
verbosity
'loquacity' is the definition.
(thesaurus)
'brevity so different' is the wordplay.
'different' is an anagram indicator.
'brevity'+'so'='brevityso'
'brevityso' with letters rearranged gives 'VERBOSITY'.
'to' acts as a link.
(Other definitions for verbosity that I've seen before include "Wordiness" , "in so many words." , "Long-windedness" .)