The trick is to incorporate Holbein's name into cabaret song in Montmartre (7)
I believe the answer is:
chanson
'cabaret song in montmartre' is the definition.
I can't judge whether this defines the answer.
'the trick is to incorporate holbein's name' is the wordplay.
'the trick' becomes 'con' (a con is a fraud or trick).
'is to incorporate' indicates putting letters inside.
'holbein's name' becomes 'hans' (I am not sure about this - if you are sure you should believe this answer much more).
'con' going around 'hans' is 'CHANSON'.
'into' is the link.
Can you help me to learn more?
(Other definitions for chanson that I've seen before include "A number" , "song for Piaf?" , "(French) song" .)