Perfect but inconclusive thought (4)
I believe the answer is:
idea
'perfect but inconclusive thought' is the definition.
'idea' can be an answer for 'thought' (idea is a kind of thought). I am unsure of the 'perfect but inconclusive' bit.
'inconclusive thought' is the wordplay.
'inconclusive' means to remove the last letter.
'thought' becomes 'ideal' (ideal is a kind of thought).
'ideal' with its final letter taken off is 'IDEA'.
Can you help me to learn more?
(Other definitions for idea that I've seen before include "Thought, belief" , "Thought; concept" , "Theory" , "Flash of inspiration?" , "Clue" .)