What's left outside entrance to major art museum (9)
I believe the answer is:
hermitage
'major art museum' is the definition.
(Russian art museum)
'what's left outside entrance to' is the wordplay.
'what's left' becomes 'heritage' (what's left by previous generations).
'outside' indicates putting letters inside.
'entrance to' becomes 'm' (I can't justify this - if you can you should give a lot more credence to this answer).
'heritage' placed around 'm' is 'HERMITAGE'.
Can you help me to learn more?
(Other definitions for hermitage that I've seen before include "St Petersburg museum - Rhone wine" , "Secluded retreat" , "art museum" , "Recluse's abode" , "accommodation for one" .)