What does the cryptic crossword clue "Grim-sounding character therefore upset? (4)" mean?

The definition is "upset?". The wordplay uses a reversal. ERGO (reversal="=therefore") = OGRE; definition: "upset?" The answer is OGRE.

Grim-sounding character therefore upset? (4)

Independent Cryptic #11927 | 1 Down | 2024-12-31 flower