Person, mellow, back in wine shop (6)
I believe the answer is:
bodega
'wine shop' is the definition.
(I've seen this before)
'person mellow back' is the wordplay.
'person' becomes 'bod' (bod can informally mean a person or body).
'mellow' becomes 'age' (both can mean to mature).
'back' is a reversal indicator.
'age' in reverse letter order is 'ega'.
'bod'+'ega'='BODEGA'
'in' acts as a link.
(Other definitions for bodega that I've seen before include "Small Hispanic wine-shop" , "Wine-shop in a Spanish-speaking country" , "Small Spanish grocery and wine store" , "Shop or cellar in Spain for selling wine" , "Liquor store" .)