Small wine jar (5)
I believe the answer is:
shock
'jar' is the definition.
(thesaurus)
'small wine' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'wine' becomes 'hock' (hock is a kind of wine).
's'+'hock'='SHOCK'
(Other definitions for shock that I've seen before include "Trauma" , "See 18" , "Jar" , "Sudden upset; offend" , "Unpleasant surprise" .)