Sounds like small bottle is disgusting (4)
I believe the answer is:
vile
'is disgusting' is the definition.
(I've seen this before)
'sounds like small bottle' is the wordplay.
'sounds like' indicates a 'sounds like' (homophone) clue.
'small bottle' becomes 'vial' (I've seen this in another clue).
'vial' sounds like 'VILE'.
(Other definitions for vile that I've seen before include "Horrible" , "Loathsome - draw veil over it" , "Live in degenerate way" , "Base" , "Disgusting kind of evil" .)