Clue: Measure that monitors monitors? (6,4)
Answer: SCREEN SIZE
Explanation: Definition: Measure
Please tell me that I am missing out on something. If this is the right answer, it looks like a charade of SCREENS ('the first 'monitors') plus IZE, an unannounced homophone of EYES ('monitors'). The definition is not too hot, either, even if it is extended. Perhaps I am over-analysing in looking for a wordplay, and the clue was intended as just a cryptic definition. In that case, the first 'monitors' would be a verb, and chosen for the repetition rather than its meaning. *The (marginally better, in my opinion) solution is SCREEN TIME*.