That's to cover magazine representation (5)
I believe the answer is:
image
'representation' is the definition.
(image is a kind of representation)
'that's to cover magazine' is the wordplay.
'that's' becomes 'ie'.
'to cover' indicates putting letters inside.
'magazine' becomes 'mag' (abbreviation for magazine).
'ie' going around 'mag' is 'IMAGE'.
(Other definitions for image that I've seen before include "Photo or likeness" , "Portrait, picture" , "Visible representation" , "Likeness; metaphor" , "Likeness, might be spitting" .)