Fashionable arrangement of facts (4)
I believe the answer is:
info
'facts' is the definition.
(I've seen this in another clue)
'fashionable arrangement of' is the wordplay.
'fashionable' becomes 'in' (in can mean fashionable or trendy).
'arrangement' is an anagram indicator.
'of' with letters rearranged gives 'fo'.
'in'+'fo'='INFO'
(Other definitions for info that I've seen before include "Data (abbrev.)" , "Data received and understood (abbr)" , "Dope" , "Intelligence (abbr)" , "details" .)