Thinking that is coherent and logical (9)
I believe the answer is:
reasoning
'thinking that is coherent and logical' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for reasoning that I've seen before include "Thinking that is coherent and logical" , "Logical thought process" , "Thinking coherently and logically" , "Debating" , "Train of thought" .)