Smashing fellow, potentially, left behind London attraction (6)
I believe the answer is:
vandal
'london attraction' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'smashing fellow potentially left behind' is the wordplay.
'smashing fellow potentially' becomes 'vanda' (I can't explain this - if you can you should give a lot more credence to this answer).
'left' becomes 'l' (common abbreviation).
'behind' says to put letters next to each other.
'vanda'+'l'='VANDAL'
Can you help me to learn more?
(Other definitions for vandal that I've seen before include "Barbarian - wrecker" , "Cultural destroyer" , "Destructive person" , "Wanton wrecker" , "Person causing wanton damage" .)