What does the cryptic crossword clue "Somewhat useful sterling area that's partly in the EU (6)" mean?

The definition is "area that’s partly in the EU". The wordplay uses a hidden word. Hidden (‘somewhat’) in usefUL STERling The answer is ULSTER.

Somewhat useful sterling area that's partly in the EU (6)

Independent Cryptic #11520 | 20 Down | 2023-09-13 flower