What does the cryptic crossword clue "Barons unhappy with a dinner in US city (3,10)" mean?

The wordplay uses an anagram. anagram of BARONS + A + DINNER = SANBERNARDINO The answer is SANBERNARDINO.

Barons unhappy with a dinner in US city (3,10)

Independent Cryptic #11719 | 24 Across | 2024-05-02 flower