Availing oneself of when ushering her out (5)
I believe the answer is:
using
'availing oneself of' is the definition.
(I've seen this in another clue)
'ushering her out' is the wordplay.
'out' is a deletion indicator.
'ushering' with 'her' taken away is 'USING'.
'when' is the link.
(Other definitions for using that I've seen before include "Putting to a particular purpose" , "addiction" , "Utilising" , "Exploiting for one's own advantage" , "Putting into service" .)