Could this drink be nastier? (7)
I believe the answer is:
retsina
'could this drink' is the definition.
'retsina' can be an answer for 'drink' (retsina is a kind of drink). I am unsure of the remainder of the definition.
'nastier?' is the wordplay.
'nastier' anagrams to 'RETSINA'.
However, I am not clear how this is indicated.
'be' acts as a link.
Can you help me to learn more?
(Other definitions for retsina that I've seen before include "Greek drink" , "Type of Greek wine" , "Nastier (anag) - white (or rose) wine" , "Greek white wine flavoured with resin" , "Nastier (anag) - Greek wine" .)