What does the cryptic crossword clue "Only diaspora where outsiders lost in old kingdom (5)" mean?

The wordplay uses a container (one word inside another). LY (synonym="LY") + DIA (synonym="DIA") = LYDIA The answer is LYDIA.

Only diaspora where outsiders lost in old kingdom (5)

Guardian Cryptic #29504 | 9 Across | 2024-10-03 flower