Writer of a sort of card with love to Victor (6)
I believe the answer is:
asimov
'writer' is the definition.
(Isaac Asimov)
'a sort of card with love to victor' is the wordplay.
'sort of card' becomes 'sim' (as in a SIM card).
'with' is a charade indicator (letters next to each other).
'love' becomes 'o' (love means zero in tennis).
'to victor' becomes 'V' (phonetic alphabet: alpha, bravo, charlie etc.).
'a'+'sim'+'o'+'v'='ASIMOV'
'of' acts as a link.
(Other definitions for asimov that I've seen before include "Author of "Three Laws of Robotics"" , "Isaac - - , SF writer" , "Isaac --, science fiction author" , "See 22 Down" , "Isaac ---, SF author" .)