I want to use my SouthWest Trains Gold Service ticket on a Friday
afternoon. (This is the free weekend travel one).

T&C includes "This ticket is not valid for travel from London Waterloo
or Clapham Junction on trains departing between 1600 and 1900
inclusive on Fridays".

I want to travel get the 1620 to Exeter Central from Waterloo.

Is the interpretation of the T&C that I can't travel using the ticket
from Waterloo, but I could buy a ticket to Woking, then use my Gold
Pass from there? Or is it any train that starts from Waterloo/CLJ
between those times, no matter where on SWT I join?

Thanks in advance.