What does the cryptic crossword clue "What 2 might produce – The 19 Down? (6)" mean?

The definition is "What 2 might produce – The 19 Down?". The wordplay uses a double definition. Double definition The answer is LETTER.

What 2 might produce – The 19 Down? (6)

Guardian Cryptic #29571 | 4 Down | 2024-12-20 flower