Impressive electronic photograph (4)
I believe the answer is:
epic
'impressive' is the definition.
(epic can mean grand or impressive)
'electronic photograph' is the wordplay.
'electronic' becomes 'e' (as in e-mail or e-books).
'photograph' becomes 'pic' (short for picture).
'e'+'pic'='EPIC'
(Other definitions for epic that I've seen before include "Long poem set in nice picture" , "Impressive scope" , "On a grand scale, like heroic poem" , "Long adventure story" , "eg The Iliad" .)