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' indicates putting letters inside.
'publicity' becomes 'ad' (short for advert).
'sly' going around 'ad' is 'SADLY'.
(Other definitions for sadly that I've seen before include "Regrettably" , "With sorrow" , "Alas" , "Lamentably, unfortunately" , "Mournfully" .)