Combat Master 2011 Rear Sight Loose

[DOBBO45]

The rear sights are loose on my TT combat master 2011 ,they wobble a little and i am worried about losing them. Is this a simple fix ( i have not had an airsoft pistol apart before) i presume i need to get to the underside of the slide below the sight? 

Any pointers appreciated 

Ok sorted it, non original rear sight and its not a perfect fit , plan b?

 

[Cr0-Magnon]

Is there a screw in the top? If so, remove it, coat in loctite blue and screw back in firmly but don't overdo it. Leave it 24hrs to completely dry.