Joy beheaded family member (7)
I believe the answer is:
elation
'joy' is the definition.
(I know that elation is a type of joy)
'beheaded family member' is the wordplay.
'beheaded' means to remove the first letter (the head of the word is removed).
'family member' becomes 'relation' (a relation or relative).
'relation' with its initial letter removed is 'ELATION'.
(Other definitions for elation that I've seen before include "Feeling of joy from toenail" , "High feeling?" , "Toenail (anag) -- delight" , "'High spirits, exhilaration (7)'" , "Bliss" .)