Place of work no longer slipping? (6)
I believe the answer is:
office
'place of work' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
(Other definitions for office that I've seen before include "Professional or clerical duties are performed here" , "Subsidiary" , "Workplace for white-collar workers" , "Where many of us work" , "Where a white-collar worker works" .)