Marketplace at side of garage — park here (4)
I believe the answer is:
ebay
'marketplace' is the definition.
(I have seen 'Online marketplace' mean 'ebay' so perhaps 'marketplace' could also mean 'ebay')
'at side of garage park here' is the wordplay.
'at' says to put letters next to each other.
'side of' says to take the final letters.
'park here' becomes 'bay' (I can't explain this - if you can you should give a lot more credence to this answer).
The final letter of 'garage' is 'e'.
'e'+'bay' is 'EBAY'.
Can you help me to learn more?
(Other definitions for ebay that I've seen before include "Modern marketplace" , "Online market" , "Auction site" , "Website" , "Internet sales facility" .)