Yap.Town

の会員だ

is a member of

→ の
phrase Rare #30,551
is a member of The の connects the group or organization to 会員 (member). だ is the plain-form equivalent of です.
JA: 彼はこのクラブの会員だ。
EN: He is a member of this club.

トムは読書会の会員だ。

Tom is a member of the book club.

トムは全米ライフル協会の会員だ。

Tom is a member of the National Rifle Association.

メアリーは読書会の会員だ。

Mary is a member of the book club.