I smell from the bottom, a fetish (3)
I believe the answer is:
obi
'a fetish' is the definition.
(fetish or charm in obi or obeah witchcraft)
'i smell from the bottom' is the wordplay.
'smell' becomes 'B.O.' (abbreviation for Body Odour).
'from the bottom' shows that the letters should be reversed in order (in a down clue, letters come from the bottom).
'i'+'bo'='ibo'
'ibo' reversed gives 'OBI'.
(Other definitions for obi that I've seen before include "Japanese dress" , "Charm used in witchcraft" , "Form of witchcraft" , "Martial arts sash" , "Caribbean's charming" .)