Small bottle contributing to conviviality (4)
I believe the answer is:
vial
'small bottle' is the definition.
(I've seen this in another clue)
'contributing to conviviality' is the wordplay.
'contributing to' indicates the answer is hidden within the clue (the answer contributes to part of the clue ).
'VIAL' can be found hidden inside 'conviviality'.
(Other definitions for vial that I've seen before include "Small glass container" , "Ampoule" , "Small container for liquid medicine" , "Small bottle used for medicines, laboratory work, etc" , "Small container for liquids" .)