Fawning host supporting sadomasochism (6)
I believe the answer is:
smarmy
'fawning' is the definition.
(I've seen this before)
'host supporting sadomasochism' is the wordplay.
'host' becomes 'army' (both can mean a large number of people).
'supporting' says to put letters next to each other (in a down clue, some letters go below others).
'sadomasochism' becomes 'sm' (S and M).
'army' after 'sm' is 'SMARMY'.
(Other definitions for smarmy that I've seen before include "Unctuous" , "Slick" , "Bootlicking" , "Oleaginous" , "Conceal oneself" .)