Electronic tag left in coat (6)
I believe the answer is:
enamel
'coat' is the definition.
(I know that enamel is a type of paint)
'electronic tag left' is the wordplay.
'electronic' becomes 'e' (as in e-mail or e-books).
'tag' becomes 'name' (I've seen this in another clue).
'left' becomes 'l' (common abbreviation).
'e'+'name'+'l'='ENAMEL'
'in' acts as a link.
(Other definitions for enamel that I've seen before include "Hard white substance covering the crown of a tooth" , "Hard shiny coating as on teeth" , "protective coat" , "Glassy substance" , "art form" .)