Seems to work:

[126] pry(main)> cte.apply_to(base.model.all).first
  Clusters::Cluster Load (2.0ms)  WITH RECURSIVE "base_and_ancestors" AS (SELECT clusters.*, namespaces.parent_id AS group_parent_id FROM "clusters" INNER JOIN "cluster_groups" ON "cluster_groups"."cluster_id" = "clusters"."id" INNER JOIN "namespaces" ON "namespaces"."id" = "cluster_groups"."group_id" AND "namespaces"."type" IN ('Group') WHERE "namespaces"."type" IN ('Group') AND "namespaces"."id" = 60
UNION
SELECT clusters.*, namespaces.parent_id AS group_parent_id FROM "base_and_ancestors", "clusters" INNER JOIN "cluster_groups" ON "cluster_groups"."cluster_id" = "clusters"."id" INNER JOIN "namespaces" ON "namespaces"."id" = "cluster_groups"."group_id" AND "namespaces"."type" IN ('Group') WHERE "namespaces"."id" = "base_and_ancestors"."group_parent_id") SELECT  "clusters".* FROM "base_and_ancestors" AS "clusters" ORDER BY "clusters"."id" ASC LIMIT $1  [["LIMIT", 1]]
  ↳ (pry):125
=> #<Clusters::Cluster:0x00007fb327a80bd8
 id: 43,
 user_id: 1,
 provider_type: "user",
 platform_type: "kubernetes",
 created_at: Thu, 20 Jun 2019 11:11:31 UTC +00:00,
 updated_at: Thu, 20 Jun 2019 11:11:31 UTC +00:00,
 enabled: true,
 name: "woww",
 environment_scope: "*",
 cluster_type: "group_type",
 domain: nil,
 managed: false>

[133] pry(main)> cte.apply_to(base.model.all).first.group

=> #<Group id:60 @hello/woww>

[134] pry(main)> cte.apply_to(base.model.all).last
  Clusters::Cluster Load (1.5ms)  WITH RECURSIVE "base_and_ancestors" AS (SELECT clusters.*, namespaces.parent_id AS group_parent_id FROM "clusters" INNER JOIN "cluster_groups" ON "cluster_groups"."cluster_id" = "clusters"."id" INNER JOIN "namespaces" ON "namespaces"."id" = "cluster_groups"."group_id" AND "namespaces"."type" IN ('Group') WHERE "namespaces"."type" IN ('Group') AND "namespaces"."id" = 60
UNION
SELECT clusters.*, namespaces.parent_id AS group_parent_id FROM "base_and_ancestors", "clusters" INNER JOIN "cluster_groups" ON "cluster_groups"."cluster_id" = "clusters"."id" INNER JOIN "namespaces" ON "namespaces"."id" = "cluster_groups"."group_id" AND "namespaces"."type" IN ('Group') WHERE "namespaces"."id" = "base_and_ancestors"."group_parent_id") SELECT  "clusters".* FROM "base_and_ancestors" AS "clusters" ORDER BY "clusters"."id" DESC LIMIT $1  [["LIMIT", 1]]
  ↳ (pry):132
=> #<Clusters::Cluster:0x00007fb323ddeb30
 id: 44,
 user_id: 1,
 provider_type: "user",
 platform_type: "kubernetes",
 created_at: Thu, 20 Jun 2019 11:11:45 UTC +00:00,
 updated_at: Thu, 20 Jun 2019 11:11:45 UTC +00:00,
 enabled: true,
 name: "hello",
 environment_scope: "*",
 cluster_type: "group_type",
 domain: nil,
 managed: false>

[135] pry(main)> cte.apply_to(base.model.all).last.group

=> #<Group id:59 @hello>

https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/gitlab/project_authorizations/with_nested_groups.rb is a good example