What does the cryptic crossword clue "Ongoing relief devised for a corps with volunteers (7,6)" mean?

The wordplay uses an anagram. anagram of ONGOING + RELIEF = FOREIGNLEGION The answer is FOREIGNLEGION.

Ongoing relief devised for a corps with volunteers (7,6)

Daily Mail Cryptic #17139 | 19 Across | 2023-07-12 flower