What is the root word (Mool Shabd) in the word 'Khilona'?

The noun word 'Khilona' (खिलौना) is formed by attaching the suffix (Pratyay) 'Auna' (औना) to the root verb base word 'Khel' (खेल).
$$\text{खेल}+\text{औना}=\text{खिलौना}$$