Pie collar
A pie collar is a strip or ring of aluminium foil placed over the exposed rim of a pie during baking to shield the crust edge from direct heat and stop it browning before the rest of the pie is done.
The rim of a pie is thin and fully exposed, so it colours faster than the lid or base. Fit the collar loosely, either as a folded strip crimped around the edge or as a foil ring with the centre cut out, and add it once the rim is golden, usually halfway through baking.
Reusable silicone crust shields do the same job and are easier to fit. Whichever you use, do not press it tightly onto the pastry or it will steam the edge soft instead of protecting it.