Workers in tandem work on change for the better (9)
I believe the answer is:
amendment
'change for the better' is the definition.
(I've seen this before)
'workers in tandem work' is the wordplay.
'workers' becomes 'men' (men can mean staff or employees).
'in' means one lot of letters goes inside another.
'work' indicates an anagram.
'tandem' anagrammed gives 'amendt'.
'men' inserted within 'amendt' is 'AMENDMENT'.
'on' acts as a link.
(Other definitions for amendment that I've seen before include "Alteration made in a formal document" , "Minor improvement" , "Statement added to or revising a document" , "a bit of a change!" , "the fifth one benefiting Uncle Sam's defendants?" .)