Opening a chapter in deep affection (6)
I believe the answer is:
alcove
'opening' is the definition.
(opening or recess in a building)
'a chapter in deep affection' is the wordplay.
'chapter' becomes 'c'.
'in' indicates putting letters inside.
'deep affection' becomes 'love' (I've seen this before).
'c' inserted within 'love' is 'lcove'.
'a'+'lcove'='ALCOVE'
(Other definitions for alcove that I've seen before include "A small recess or niche" , "sheltered spot" , "Recess in a small room or wall" , "Recessed part of a room" , "bay" .)