Delight in kinsman losing head (7)
I believe the answer is:
elation
'delight' is the definition.
(I've seen this before)
'kinsman losing head' is the wordplay.
'kinsman' becomes 'relation' (I've seen this in another clue).
'losing head' means to remove the first letter.
'relation' with its first letter taken off is 'ELATION'.
'in' acts as a link.
(Other definitions for elation that I've seen before include "State of pleasure about toe-nail" , "Feeling of joy for it alone" , "State of being delighted or proud" , "Feeling of delight, joy" , "It's a great feeling!" .)