You want to re-use a wall plug that's already in the wall, but it's too large and you can't get your screw to knit with it.
You will need
Step by step process
Ensure the area is clean, dry and free from oil, dust and grease.
Remove the Polycell Plug & Fix Polyfilla from the packet and cut off a strip.
Remove the protective film from both sides of this strip and then knead it - make sure you wear suitable gloves. It may help if you wet the Polyfilla with a little water.
Once it is uniform in colour, push into the raw plug cavity using a flat bladed tool until it is fully filled. Polycell Plug & Fix remains workable for up to 4 minutes, which should give you ample time to remove any excess material and ensure a flush finish.
Insert your screw into the Polyfilla. Screw to around half-way using light finger pressure. This will create a pilot hole.
Leave the screw in place to set for one hour, then use a screwdriver to carefully remove it. The screw can then be replaced and fully tightened when you're ready. Polycell Plug & Fix Polyfilla can support hanging objects of up to 30kg.