No problem mate.
Riding the clutch, even minimally, which is almost inevitable in slow moving traffic, may well point towards an excessively worn clutch plate or Flywheel and the difficulty either of them may be having trying to re-engage, but any mechanical will tell you to continue as you are until the clutch starts slipping or goes completely.
The subframe bolts having loosened off is also a possibility, but usually it's only identifiable in left to right turns or vice versa. I've never heard of it on clutch release or coming to a stop.
Another thing it may be is an engine or transmission mount, some times the rubber bushes get worn and the play becomes excessive causing the metal to knock. What you're describing could easily be that.
What I would say is, don't think worse case scenario, because it probably isn't. We all do it, but it's usually always unjustified.
