Cocktail party above saloon perhaps (7)
I believe the answer is:
sidecar
'cocktail' is the definition.
(I know that Sidecar is a type of cocktail)
'party above saloon perhaps' is the wordplay.
'party' becomes 'side' (eg a side or party in a contract).
'above' says to put letters next to each other (in a down clue, some letters go above others).
'saloon perhaps' becomes 'car' (I've seen this before).
'side'+'car'='SIDECAR'
(Other definitions for sidecar that I've seen before include "Motorcycle addition" , "Cocktail - which some motor-cyclists get attached to?" , "passenger compartment" , "Motorbike passenger attachment" , "Cocktail of brandy, orange liqueur and lemon juice" .)