Mobile places stocking new glass protector (4,3)
I believe the answer is:
lens cap
'glass protector' is the definition.
(I've seen this in another clue)
'mobile places stocking new' is the wordplay.
'mobile' indicates an anagram (mobile can mean moving).
'stocking' is an insertion indicator ('stock' can mean 'carry' or 'contain').
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'places' with letters rearranged gives 'lescap'.
'lescap' placed around 'n' is 'LENS CAP'.
(Other definitions for lens cap that I've seen before include "Aperture protector" , "protection for photographer" , "Camera cover" .)