Crossword Genius

Where to shop for a thousand of everything? (4)

Ross

I believe the answer is:

mall

I'm a little stuck... Click here to teach me about this clue!

Here is my best explanation:

'where to shop' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.

'a thousand of everything?' is the wordplay.
'a thousand of' becomes 'm' (I can't justify this - if you can you should believe this answer much more).
'everything?' becomes 'all' (I've seen this before).
'm'+'all'='MALL'

'for' acts as a link.

Can you help me to learn more?

This clue was last seen in Evening Standard