Pictures seen one million times (6)
I believe the answer is:
images
'pictures' is the definition.
('image' can be a synonym of 'picture')
'one million times' is the wordplay.
'one million' becomes 'im' (resembles 1m).
'times' becomes 'ages' (age is a kind of time).
'im'+'ages'='IMAGES'
'seen' acts as a link.
(Other definitions for images that I've seen before include "Pictures or photos" , "Pictures, representations" , "Photos or representations" , "Visual or mental representations" , "Likenesses, representations" .)