... start to study unopened red wine (6)
I believe the answer is:
sherry
'wine' is the definition.
(sherry is a kind of wine)
'start to study unopened red' is the wordplay.
'start to' indicates taking the first letters.
'unopened' means to remove the first letter.
'red' becomes 'cherry' (shade of red).
The initial letter of 'study' is 's'.
'cherry' with its first letter taken off is 'herry'.
's'+'herry'='SHERRY'
(Other definitions for sherry that I've seen before include "Spanish drink" , "Fortified wine from Jerez" , "Fortified wine as aperitif" , "Jerez drink" , "Pre-dinner aperitif as from Jerez" .)