Hand down to father's next of kin (4,2)
I believe the answer is:
pass on
'hand down' is the definition.
(I've seen this in another clue)
'father's next of kin' is the wordplay.
'father's' becomes 'pa's' (pa can mean dad or father).
'next of kin' becomes 'son' (I can't explain this - if you can you should believe this answer much more).
'pas'+'son'='PASS ON'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for pass on that I've seen before include "go forward" , "Bequeath" , "Refuse" , "Hand over - die" .)