Top of the heap? Reckon reported wine collection is about second (10)

I believe the answer is:
bestseller
'top of the heap? reckon' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'reported wine collection is about second' is the wordplay.
'reported' indicates a 'sounds like' (homophone) clue.
'wine collection' becomes 'cellar'.
'is about' means one lot of letters go next to another.
'second' becomes 'best' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'cellar' is a homophone of 'seller'.
'seller' put after 'best' is 'BESTSELLER'.
Can you help me to learn more?
(Other definitions for bestseller that I've seen before include "Dickens for instance" , "top author" .)