Get better workers in a time leading to change (9)
I believe the answer is:
Here is my best explanation:
'change' is the definition.
(amendment is a kind of change)
'get better workers in a time leading' is the subsidiary indication.
'get better' becomes 'mend' ('mend' can be a synonym of 'get better').
'workers' becomes 'men' (man is a kind of worker).
'in' indicates putting letters inside.
'leading' suggests taking the first letters.
The initial letter of 'time' is 't'.
'mendmen' placed into 'at' is 'amendment'.
'to' is the link.
(Other definitions for amendment that I've seen before include "Addition or alteration, to a motion or official document, say", "Statement added to or revising a document", "Minor improvement", "Change designed to improve a text", "Alteration made in a formal document" and "Correction".)