Unctuous host pursuing controlling sex (6)
I believe the answer is:
smarmy
'unctuous' is the definition.
(I know that unctuous can be written as smarmy)
'host pursuing controlling sex' is the wordplay.
'host' becomes 'army' (I've seen this before).
'pursuing' means one lot of letters go next to another.
'controlling sex' becomes 'sm' (I can't justify this - if you can you should give a lot more credence to this answer).
'army' put after 'sm' is 'SMARMY'.
Can you help me to learn more?
(Other definitions for smarmy that I've seen before include "Oily" , "Unctuous" , "Bootlicking" , "Conceal oneself" , "Excessively flattering (R, not L)" .)