In bed here knight not delirious (8)
I believe the answer is:
coherent
'not delirious' is the definition.
I can't judge whether this defines the answer.
'in bed here knight' is the wordplay.
'in' means one lot of letters goes inside another.
'bed' becomes 'cot' (cot is a kind of bed).
'knight' becomes 'N' (chess abbreviation).
'here'+'n'='heren'
'cot' enclosing 'heren' is 'COHERENT'.
Can you help me to learn more?
(Other definitions for coherent that I've seen before include "Rational" , "Clear and logical, not confused" , "Meaningful" , "Not rambling in speech or reason" , "Orderly, logical, consistent" .)