Regularly sends in rubbish, upsetting my boss (6)
I believe the answer is:
editor
'my boss' is the definition.
(the crossword setter's boss is a newspaper editor)
'regularly sends in rubbish upsetting' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'rubbish' becomes 'rot' (both can mean nonsense).
'upsetting' is a reversal indicator.
'sends'+'in'='sendsin'
The alternating letters of 'sendsin' are 'edi'.
'rot' written backwards gives 'tor'.
'edi'+'tor'='EDITOR'
(Other definitions for editor that I've seen before include "Chief journalist" , "Director of 3 down" , "Media boss" , "Rag worker" , "Do tie out the newspaper head" .)