What does the cryptic crossword clue "Some seabirds returning, or just one (4)" mean?

The definition is "just one". The wordplay uses a reversal. reverse of AUKS = SKUA; definition: "just one" The answer is SKUA.

Some seabirds returning, or just one (4)

Times Cryptic #28707 | 22 Across | 2023-09-13 flower