Fortigate ZTNA with Clearpass (Entra ID as user database)

Hi All,

I have doubt if we can achieve below requirement. 

Fortigate integrate with Clearpass/ISE for ZTNA authentication , but the user identity is at Entra ID(no local AD). 

I knew that Fortigate can direct integrate with Entra ID using SAML, but client insist to use Clearpass/ISE as authentication server(lets not challenge client why at this moment). 

Flow should be ZTNA Client > Fortigate > Clearpass/ISE > Entra ID

Question : Can this be done ? Or can i say this can be only done if FortiAuthenticator is used instead of Clearpass/ISE ?