Judges locking up workers for the first time can be seen on the tapes (12)

'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'.
'men'+'t'='ment'
'measures' enclosing 'ment' is 'measurements'.

'time' is the link.

Can you help me to learn more?