I think the term "clinical study" is broader in meaning than the term 'clinical trial'.
I think a 'clinical trial' is a clinical study to obtain approval for an investigational drug or medical device, and the notion of the 'clinical study' includes studies that are not aimed at obtaining approval.
So, 'the study to find the effect of "Azadirachta indica"' is a clinical study, but I think it is somewhat incongruous to call this a clinical trial. However, if the active ingredient is purified and then sought for approval as a drug, I think it would regarded as a clinical trial.
The website of ClinicalTrials.gov has following descriptions;
There are two main types of clinical studies: clinical trials (also called interventional studies) and observational studies. ClinicalTrials.gov includes both interventional and observational studies.
According to the description above, if it is an interventional study, it might be called a clinical trial.