Polish workers found in borders of England (5)
I believe the answer is:
emend
'polish' is the definition.
(thesaurus)
'workers found in borders of england' is the wordplay.
'workers' becomes 'men' (man is a kind of worker).
'found in' indicates putting letters inside.
'borders of' means to remove the middle letters.
'england' with its middle taken out is 'ed'.
'men' put inside 'ed' is 'EMEND'.
(Other definitions for emend that I've seen before include "Remove faults from" , "change" , "Make correction in written material" , "Remove errors" , "do editorial work" .)