Something buried in the graveyard

In the middle of the graveyard there's a patch of loose earth. Something lies underneath.
Nudge 1Where to look
Graves are dug, not opened.
Nudge 2A stronger push
A gravedigger's tool lies in a walled-in chamber at the far end of Bridge Street.
What you needOther problems to solve first
Solve these first (each opens its own page, no answers on the way):
Show the solutionThe whole answer, with a video
Drop the gravediggers muddy spade (see A walled-in chamber at the end of Bridge Street) on the loose earth: a trapdoor opens, and Dizzy drops into a small eerie cave below.