Innovative thinker once dismissing king not making sense (10)
I believe the answer is:
incoherent
'not making sense' is the definition.
'innovative thinker once dismissing king' is the wordplay.
'innovative' is an anagram indicator.
'dismissing' suggests deleting specific letters.
'king' becomes 'k'.
'thinker'+'once'='thinkeronce'
'thinkeronce' with 'k' removed is 'thineronce'.
'thineronce' is an anagram of 'INCOHERENT'.
(Other definitions for incoherent that I've seen before include "Unintelligible" , "drunk?" , "difficult to understand" , "rambling" , "Confused" .)