What could be finer to conclude? (5)
I believe the answer is:
infer
'conclude?' is the definition.
(inferring is a kind of concluding)
'what could be finer' is the wordplay.
'what could be' indicates an anagram.
'finer' anagrammed gives 'INFER'.
'to' is the link.
(Other definitions for infer that I've seen before include "Take or gather meaning from" , "Conclude or judge from facts" , "Deduce logically" , "Conjecture" , "'Deduce, conclude (5)'" .)