Cryptically, it is a busy commercial area (4,6)
I believe the answer is:
city centre
'cryptically it' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'busy commercial area' is the wordplay.
'busy commercial' becomes 'city' (I am not sure about this - if you are sure you should believe this answer much more).
'area' becomes 'centre' (centre is a kind of area).
'city'+'centre'='CITY CENTRE'
'is a' acts as a link.
Can you help me to learn more?
(Other definitions for city centre that I've seen before include "Downtown" , "metropolitan area" , "Bullring, say" , "Focal point of urban area" .)