Could anyone here help me with it? What tools should I use and what steps should I take to remove the clip and all the plastic parts including the top cap? It's probably worth mentioning that it's an FP cap.
EDIT:
OK, I think I got it. Gently pushing the plastic jewel with something of similar diameter (empty cartridge in my case) seems to do the trick

Although I pushed just a little to see if it would go. It did.