A shopkeeper? Wrong. A garage mechanic (9)
I believe the answer is:
outfitter
'a shopkeeper?' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'wrong a garage mechanic' is the wordplay.
'wrong a garage' becomes 'out' (I am not sure about this - if you are sure you should believe this answer much more).
'mechanic' becomes 'fitter' (I've seen this before).
'out'+'fitter'='OUTFITTER'
Can you help me to learn more?
(Other definitions for outfitter that I've seen before include "Seller of men's clothing" , "One dealing in clothing" , "Seller of clothes" , "Men's clothes shop" , "One supplies gear" .)