Photo that is covering periodical (5)
I believe the answer is:
image
'photo' is the definition.
(I've seen this in another clue)
'that is covering periodical' is the wordplay.
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'covering' indicates putting letters inside.
'periodical' becomes 'mag' (short for magazine).
'ie' enclosing 'mag' is 'IMAGE'.
(Other definitions for image that I've seen before include "Picture (involving one letter change from 10)" , "Likeness, could be spitting" , "Representation of person or thing" , "Likeness or mental picture" , "Dead ringer" .)