Deduce it's a finer arrangement (5)
I believe the answer is:
infer
'deduce' is the definition.
(synonyms)
'a finer arrangement' is the wordplay.
'arrangement' indicates an anagram.
'finer' is an anagram of 'INFER'.
'it's' is the link.
(Other definitions for infer that I've seen before include "Extrapolate, conclude" , "Deduce logically" , "Deduce (from evidence)" , "Draw a conclusion" , "'Deduce, conclude (5)'" .)