Frank refines temperature
I believe the answer is:
honest
'frank' is the definition.
(similar in meaning)
'refines temperature' is the wordplay.
'refines' becomes 'hones' (I've seen this in another clue).
'temperature' becomes 't' (abbreviation).
'hones'+'t'='HONEST'
(Other definitions for honest that I've seen before include "Not dissembling" , "Fair and free of deceit" , "Law-abiding" , "Honorable, true" , "Fair and square" .)