Old-fashioned heir dies (6,2)
I believe the answer is:
passes on
'dies' is the definition.
(I've seen this before)
'old-fashioned heir' is the wordplay.
'old-fashioned' becomes 'passe' (synonyms).
'heir' becomes 'son' (I've seen this before).
'passe'+'son'='PASSES ON'
(Other definitions for passes on that I've seen before include "Dies; transmits" , "graduates" , "Hands to the next person" .)