Hello student yes you can appear in Neet entrance examination even if you've failed in one subject as appearing Candidates are also eligible for Neet entrance examination but you need to pass our compartment examination before the counseling process, so if you are want you can appear for compartment examination in your CHSE board or you can also appear in NIOS on demand examination.

Eligibility - Candidates must passed or appearing class 12 in Physics chemistry and biology with minimum 50 percent marks aggregate from a recognized board.

For more details refer to the link mentioned below - https://www.google.com/amp/s/medicine.careers360.com/articles/neet-eligibility-criteria/amp

Feel free to comment if you've any doubt

Good luck