What does the cryptic crossword clue "Doing brilliantly, confronting leader to be deposed (5)" mean?

The definition is "Doing brilliantly,". The wordplay uses acrostic. ACING (deletion) = ACING; definition: "Doing brilliantly," The answer is ACING.

Doing brilliantly, confronting leader to be deposed (5)

Guardian Cryptic #28972 | 10 Across | 2023-01-20 flower