root@noc-01:/etc/ansible# cat test.yml
---
- hosts: all
  tasks:
    - name: Incl. var file
      include_vars: var.yml

    - name: Echo
      debug:
        msg: Ello '{{ test }}'
root@noc-01:/etc/ansible# cat var.yml
test: "{{ hostvars['10.0.0.1']['ansible_hostname'] }}"


RESULT:

TASK [Echo] ********************************************************************
ok: [10.0.0.1] => {
    "msg": "Ello 'test'"
}