Which fender clean? Tweed? Bassman? Twin or Deluxe Reverb?
I think it gets some incredibly nice cleans - MUCH better and more versatile than the Mark IV, and that it can get in the ballpark of any of the most popular fender clean styles I mention above.
I've only played one authentic 50's Fender tweed, and that was only for 20 takes on one solo - but there's something about the tweed mode that actually does harken back to that amp that I played.
My Traynor Bassmate is now tweaked a little more Plexi than Bassman, but the Mark IV does get pretty close to the tones that I dial into that amp aswell. The last 10% is all taste of course.
At rehearsal, the other guitar player is going through a Hotrod Deluxe, but I'm dialed in very differently than him for the sake of separation of tones... one day I should bring my A/B/Y pedal and see if I can dial in a nice Deluxe sounding clean.
One thing that I found interesting a few years ago when I had a '76 silverface Twin Reverb - when I plugged my Mark IV into the combo speakers I got an amazing tone.... you can never discount all the other factors. I also find that one of the most important components of an amazing clean tone is the room that you're playing it in.