Hello aspirant

No you can't apply for neet without getting passed in class xii.

There is the provision to apply for class xii students who are freshers and studying in class xii waiting for results but it is not applicable to those who are failed .

Droppers and class improvement candidates also can apply .

You have not mentioned , in which subjects you are failed,  you may apply through NIOS , if you are failed in one or two subjects.

NIOS is National Institute of Open Schooling.  Nios marks are accepted in all universities of India and even you can appear for neet with nios marks .