Judges locking up workers for the first time can be seen on the tapes (12)
I believe the answer is:
Here is my best explanation:
'can be seen on the tapes' is the definition.
I can't tell whether this definition defines the answer.
'judges locking up workers for the first' is the subsidiary indication.
'judges' becomes 'measures' (measuring is a kind of judging**).
'locking up' indicates putting letters inside (I've seen this in other clues).
'workers' becomes 'men' (man is a kind of worker).
'for' says to put letters next to each other.
'first' indicates taking the first letters.
The first letter of 'the' is 't'.
'measures' enclosing 'ment' is 'measurements'.
'time' is the link.