Clue: Jubilant hearts lift after start of seasonal occasion in pub (2,7,6)
Answer: IN SEVENTH HEAVEN
Explanation: Definition: Jubilant
An envelope ('in') of S ('start of **S**easonal') plus EVENT ('occasion') plus H ('hearts' in bridge, say) plus HEAVE ('lift', with 'after' indicating the order of the particles) in INN ('pub').