What does the cryptic crossword clue "Xmas season to bode ill, ultimately? (4)" mean?

The definition is "Xmas". The wordplay uses acrostic. last letters of "season to bode ill," = NOEL; definition: "Xmas" The answer is NOEL.

Xmas season to bode ill, ultimately? (4)

Times Cryptic #26963 | 24 Down | 2018-02-16 flower