Understanding an address about workers (9)
I believe the answer is:
agreement
'understanding' is the definition.
(I know that understanding can be written as agreement)
'an address about workers' is the wordplay.
'an' becomes 'a'.
'address' becomes 'greet' (greeting is a kind of addressing).
'about' indicates putting letters inside.
'workers' becomes 'men' (men can mean staff or employees).
'greet' enclosing 'men' is 'greement'.
'a'+'greement'='AGREEMENT'
(Other definitions for agreement that I've seen before include "Correspondence" , "Union < matching" , "deal" , "Unlikely result" , "Pact" .)