Lifting just once a week?

depends I guess on you. if you bench, squat, and deadlift on that day and add some accessory lifts it could help maintain. I dont think you will make gains but better than nothing

IMO you should still make progress as long as you are training and eating correctly. The changes to your body aren't going to evaporate over six days between workouts as long as the rest of your life is in order.

Ultimately workout progression is limited by recovery time. The faster you recover, the sooner you work out again and the sooner you start recovering fast again etc. That's why anabolics are so effective and also why it's easier and quicker for younger, healthier people to make gains.

So yeah I think you can still make progress, it's just slower than it would be if you could workout more often and maximize your recovery time efficiency. But slow progress is still progress.

I would suggest lifting heavy if you’re just going to do once per week. Get in the 5-8rep range if you’re training for strength. I’m sure someone here can give you a better plan than I could.

To the OP, LSU777 put up a really good workout plan. Unless you are training for some type of serious competition or athletic endeavor, you should be fine paring that plan with a decent diet.

I actually believe most people (not counting the serious lifters on this board) who lift 4-6/week would be better off only lifting 2-3/week with bodyweight and flexibility work or even just other general activities on the non-lifting days. Its been better for me as I've got older and busier.