Photograph for police records (informal) (7)
(Other definitions for mug shot that I've seen before include "Photograph taken for police records" , "police will want this from him" , "Police photo" , "Passport photograph?" .)
(Other definitions for mugshot that I've seen before include "Photo of criminal" , "Photograph taken for police records" , "record made by police" , "Police snap" , "Still capturing the culprit" .)