They take pictures a hundred - a thousand - times (7)

I believe the answer is:

cameras

I'm a little stuck... Click here to teach me more about this clue!

'they take pictures a' is the definition.
The definition suggests an adverb but the answer is not.

'hundred a thousand times' is the wordplay.
'hundred' becomes 'c' (Roman numeral).
'thousand' becomes 'm' (Roman numeral for a thousand).
'times' becomes 'eras' (an era is a time or period).
'c'+'a'+'m'+'eras'='CAMERAS'

Can you help me to learn more?

(Other definitions for cameras that I've seen before include "Light-proof boxes" , "Image recorders" , "television equipment" .)

I've seen this clue in The Globe and Mail.

Want a hint initially instead of a full solution? Install my app