Laid back about English knight’s rejection of request (6)
I believe the answer is:
denial
'rejection of request' is the definition.
'laid back about english knight's' is the wordplay.
'back' says the letters should be written in reverse.
'about' is an insertion indicator.
'english' becomes 'e' (abbreviation).
'knight' becomes 'n' (chess).
'laid' reversed gives 'dial'.
'e'+'n'='en'
'dial' enclosing 'en' is 'DENIAL'.
(Other definitions for denial that I've seen before include "Refusal to believe an unacceptable truth" , "Refusal, abnegation" , "Declaration that something is untrue" , "Refusal to accept an unpalatable truth" , "Rejection or refusal" .)