Deplorably shifty about publicity (5)
I believe the answer is:
sadly
'deplorably' is the definition.
(thesaurus)
'shifty about publicity' is the wordplay.
'shifty' becomes 'sly' (I've seen this in another clue).
'about' is an insertion indicator.
'publicity' becomes 'ad' (short for advertisement).
'sly' enclosing 'ad' is 'SADLY'.
(Other definitions for sadly that I've seen before include "Regrettably" , "With sorrow" , "Alas" , "Lamentably, unfortunately" , "Mournfully" .)