O.K.
Something not right about this picture. I'm assuming you are talking about one of the barrel-bushing comps, right?
Apparently it is out of spec enough that the locking tab isn't lining up with the slide cut to release it.
Full-length guide rod, or standard recoil spring plug?
If you have a standard plug, take the slide off and get the recoil spring out of the way.
1. Pull the slide back until the slide stop lines up with the takedown notch and pop it out.
2. Now ease the slide forward and wrap your hand around it as it comes off the frame so you can keep control of the recoil spring.
3. Once off, take the spring out and push the plug back out of the way.
Now, the barrel & bushing comp should be loose so you can fiddle with it until you hit the magic combination to get it to come off.
rc