Per item (1,3)
(Other definitions for a pop that I've seen before include "individually" , "What an orphan might wish for" .)
'per item' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for each that I've seen before include "Ache (anag.)" , "...per head" , "every individual" , "Per capita, apiece" , "every one individually" .)
(Other definitions for apiece that I've seen before include "For or by each one of group" , "for everyone" , "Per person" , "A head" .)