Convinces after workers completed reform (4,4,4)
I believe the answer is:
mend ones ways
'reform' is the definition.
(to mend one's ways is to reform or improve)
'convinces after workers completed' is the wordplay.
'convinces' becomes 'sways' (I've seen this in another clue).
'after' means one lot of letters go next to another.
'workers' becomes 'men' (men can mean staff or employees).
'completed' becomes 'done' (something that's been completed has been done).
'men'+'done'='mendone'
'sways' after 'mendone' is 'MEND ONES WAYS'.
(Another definition for mend ones ways that I've seen is " reform".)