What does the cryptic crossword clue "Large group out to lunch, starter unavailable (4)" mean?

The definition is "Large group". The wordplay uses acrostic. ARMY (deletion) = ARMY; definition: "Large group" The answer is ARMY.

Large group out to lunch, starter unavailable (4)

Guardian Cryptic #29304 | 6 Across | 2024-02-13 flower