If your transmissions filter is clogged then you would get no reverse as well as no forward gears as well because the transmission fluid filter would not allow the fluid to flow freely through the transmission.
When the transmission fluid doesn't go through the transmission then the transmission would not go forward or in reverse.
So it's unlikely that the transmission filter is the cause of your no reverse in the transmission.
A cause of a transmission not going into reverse but going forward is due to a faulty transmission control solenoid.
Or the transmission bands could be bad or the transmission is about to go out and needs rebuilt.
Usually a transmission needs rebuilding if the transmission is not going into reverse because soon it may not go into forward gears.
I would take the vehicle to a transmission shop and have the transmission checked out and possibly changed out or rebuilt.