Answered by Shaykh Faraz Rabbani
Question: Tightness of Clothes
Answer: Tightness is, indeed difficult to specifically define. The tighter clothing is, the more disliked it would be–and when it is reasonably likely to attract undue looks as a result of the tightness, then it would become sinful as well.
Caution is best. This does include the legs with very high boots, though “regular” boots wouldn’t be considered disliked (as they are being worn for good reason, and aren’t typically considered “unduly attractive”).
The outer garment should be loose around the chest area, yes.
One should strive to hold oneself to the “higher” ways of greater modesty and decorum, while making excuses for others, and seeking whether we can gently and positively encourage them towards what is better.
And Allah alone gives success.