An affection includes key compartment (6)
I believe the answer is:
alcove
'compartment' is the definition.
(I've seen this before)
'an affection includes key' is the wordplay.
'an' becomes 'a'.
'affection' becomes 'love' (I've seen this before).
'includes' is an insertion indicator.
'key' becomes 'c' (I've seen this in other clues**).
'love' going around 'c' is 'lcove'.
'a'+'lcove'='ALCOVE'
(Other definitions for alcove that I've seen before include "A small recess or niche" , "bay" , "Recess in a small room or wall" , "Recessed area" , "corner" .)