What does the cryptic crossword clue "A grain's mixed up in Spanish drink (7)" mean?

The definition is "drink". The wordplay uses an anagram. anagram of A + GRAIN'S = SANGRIA; definition: "drink" The answer is SANGRIA.

A grain's mixed up in Spanish drink (7)

Daily Mail Cryptic #16979 | 4 Down | 2022-11-30 flower