Author’s earnings from connections with ruling families (9)
I believe the answer is:
royalties
'author's earnings' is the definition.
(payments to an author for each book sold)
'connections with ruling families' is the wordplay.
'connections' becomes 'ties' (tie is a kind of connection).
'with' says to put letters next to each other.
'ruling families' becomes 'royal' (royal families).
'ties' put after 'royal' is 'ROYALTIES'.
'from' acts as a link.
(Other definitions for royalties that I've seen before include "Appropriate payments" , "Writer's payments" , "Payments to composers" .)