A favourite store? (3,4)
I believe the answer is:
pet shop
'a favourite store?' is the definition.
'pet shop' can be an answer for 'store?' (pet shop is a kind of store). I'm not sure about the 'a favourite' bit.
'favourite store?' is the wordplay.
'favourite' becomes 'pet' ('pet' can be a synonym of 'favourite').
'store?' becomes 'shop' ('shop' can be a synonym of 'store').
'pet'+'shop'='PET SHOP'
Can you help me to learn more?
(Other definitions for pet shop that I've seen before include "Scene of boys and cat food" , "Source of leads" , "Where to buy hamsters - boys!" , "Boys in group" , "Where to buy hamsters and gerbils?" .)