A new notion for the Merchant of Venice (7)
I believe the answer is:
antonio
'the merchant of venice' is the definition.
(I've seen this in another clue)
'a new notion' is the wordplay.
'new' is an anagram indicator.
'notion' anagrammed gives 'ntonio'.
'a'+'ntonio'='ANTONIO'
'for' acts as a link.
(Other definitions for antonio that I've seen before include "Shakespearean merchant" , "sea captain in Twelfth Night" , "Italian chap" , "Portia's client" , "Name of the Merchant of Venice who borrowed money" .)