Clue: Start to party with new hot tub at house? (4,3,4,3)
Answer: PUSH THE BOAT OUT
Explanation: Definition: Start to party
 **1st letter of**(Start to) "party" **plus**(with) **anagram of**(new) HOT TUB AT HOUSE.
Defn: To throw a party at extravagant expense to celebrate an event – installation of a new hot tub, perhaps).