Sickeningly obsequious (7)
I believe the answer is:
fulsome
'sickeningly obsequious' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for fulsome that I've seen before include "Excessively ingratiating - of mules (anag)" , "Sickeningly obsequious" , "Excessively flattering (praise)" , "Generous, abundant" , "Excessive (praise)" .)