Clear thinking with good fortune capturing thicko with no love for king (8)
I believe the answer is:
lucidity
'good fortune capturing thicko with no love for king' is the definition.
I can't tell whether this defines the answer.
'clear thinking' is the wordplay.
'clear' becomes 'lucid' ('lucid' can be similar in meaning to 'clear').
'thinking' becomes 'ity' (I am not sure about this - if you are sure you should believe this answer much more).
'lucid'+'ity'='LUCIDITY'
'with' is the link.
Can you help me to learn more?
(Other definitions for lucidity that I've seen before include "Clearness" , "Brilliance - explicitness" , "Clarity of expression" , "Clarity (of thought)" .)