Refuse 500 yen for working (4)
I believe the answer is:
deny
'refuse' is the definition.
(I know that refuse can be written as deny)
'500 yen for working' is the wordplay.
'500' becomes 'd' (Roman numeral for 500).
'for working' indicates an anagram.
'yen' is an anagram of 'eny'.
'd'+'eny'='DENY'
(Other definitions for deny that I've seen before include "Refuse; repudiate" , "Refuse to acknowledge" , "Controvert" , "Refuse to admit the truth" , "Repudiate, disavow" .)