の服

...’s clothes

→ の
phrase Common #4,652
...’s clothes の connects a noun to 服, indicating whose clothes they are or what kind of clothes they are, such as 男の服 (men’s clothes) or 別の服 (different clothes).
JA: これは姉の服です。
EN: These are my older sister’s clothes.

流行遅れの服でも

Even if it’s out-of-fashion clothing?

— アバウト・タイム ~愛おしい時間について~ (2013)

女の子の服

Those are girls’ clothes!

— 天空の城ラピュタ (1986)

彼女はウールの服を着ていた

She was wearing woolen clothes.

を買いに行くの服がない

I have nothing to wear when I go clothes shopping.

メアリーの服地味

Mary’s clothes are rather plain.

いや学生時代の服

No, these are clothes I wore when I was a student.

— レベッカ (1940)