Rule out chapter in introduction (8)
I believe the answer is:
preclude
'rule out' is the definition.
(synonyms)
'chapter in introduction' is the wordplay.
'chapter' becomes 'c' (abbreviation).
'in' is an insertion indicator.
'introduction' becomes 'prelude' (I've seen this in another clue).
'c' placed inside 'prelude' is 'PRECLUDE'.
(Other definitions for preclude that I've seen before include "Debar" , "Prevent, forestall the possibility of" , "Prevent (something) from happening" , "'Prevent, forestall (8)'" , "Obviate, prevent" .)