Based on logic (8)
'based on logic' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rational that I've seen before include "Capable of thought" , "Of sound mind -- not a liar (anag)" , "Sensible, based on reason" , "Clear-headed" , "Using logic" .)
'based on logic' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for reasoned that I've seen before include "Dear ones (anag)" , "Debated in calm and logical way" , "Logically valid" , "made a logical case" , "Thought logically through or deduced" .)