1) Camera accessory 2) Camera attachment 3) Camera protection 4) Cause of a shot in the dark 5) Cause of some missed shots 6) Glass protector 7) It may spoil a great shot 8) Olympus protector 9) Photograph ruiner 10) Protective camera piece 11) Shot blocker 12) Type of camera cover 13) What an iPhone camera lacks 
Is a plastic, rubber or metal cover which fits over the front or back of the lens to protect it
Is a plastic, rubber or metal cover which fits over the front or back of the lens to protect it. 
[n] - cap used to keep lens free of dust when not in use
lens cover noun cap used to keep lens free of dust when not in use