Old-fashioned inheritance excluded heir (7)
I believe the answer is:
ancient
'old-fashioned' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for ancient that I've seen before include "Dating from long ago" , "showing signs of wear?" , "From the distant past" , "Very old, like some civilizations" , "Antediluvian" .)