Read, as a bar code (4)
I believe the answer is:
scan
'read as a bar code' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for scan that I've seen before include "Study the metre" , "Convert (a document) to a digital form" , "Conform to a metrical pattern" , "Scrutinize" , "Survey - examine" .)