What's the logic in thinking endlessly? (8)
I believe the answer is:
rational
'thinking endlessly?' is the definition.
'rational' can be an answer for 'thinking' (I've seen this in another clue). I am not sure about the 'endlessly?' bit.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for rational that I've seen before include "Sane and logical" , "17 [INTELLIGENT]" , "Clearly thinking" , "Agreeable to reason" , "Conforming to reason" .)