Sweetheart is one entitled to affection (8)
I believe the answer is:
ladylove
'sweetheart' is the definition.
(I know that ladylove is a type of sweetheart)
'one entitled to affection' is the wordplay.
'one entitled' becomes 'lady' (woman with an aristocratic title).
'to affection' becomes 'love' (I've seen this before).
'lady'+'love'='LADYLOVE'
'is' is the link.
(Other definitions for ladylove that I've seen before include "Female sweetheart" , "Load levy (anag.)" .)