I am a frum male and I would like to find a male tennis partner to play tennis with while I am visiting my parents in the southern USA. I was told by the local tennis instructor that I would have to attend his mixed male and female tennis clinic first where I could meet an appropriate tennis partner for me. I thought it might be immodest or inappropriate for a frum Jew with a beard to show up at a mixed tennis clinic. What do the rabonim think? Thank you.

Shalom, I think your reservations about entering the clinic are in place. I don't think any Rav can give an answer to a situation which he is not familiar with. If entering this place, there is immodesty all around, then refraining from entering such a place would be the correct thing to do, and I would advise finding some other sport for your fitness and health during your visit. If, on the other hand, there is an office area in this sports center where people are modestly dressed and that is where you want to meet, it would seem to be okay. But I cannot tell you that it all be all okay once you get there, you have to make your own judgement. However, here is a Teshuva of Rav Moshe Feinstein zt"l, (אגרות משה טו"ח ח"ב סי' מ) where he forbids entering a non-kosher restaurant even to buy something kosher, if not under extreme circumstances and there are no acquaintances of his seeing him entering. If there are acquaintances, he must explain to them the reasons for his entrance. If we should apply this in your situation, depends upon the circumstances. All the Best