According to Eric Pincus of Hoopsworld, the S&T deal for Willie Green gives Green a 3-year contract worth approximately 4.22 million dollars.
The first season is guaranteed at 1.375 million, and the final two years are non-guaranteed. In order for a player to be signed and traded, he has to receive a contract lasting a minimum of three seasons. Green likely fits into the Reggie Evans trade exception.
This deal puts the Clippers guaranteed salaries for next season at 69.01 million dollars- a little under two million under the luxury tax line. If the Clippers waive Travis Leslie and save over $500,000 on his deal, the team salary drops to 68.5 million- meaning the Clippers could acquire one more player worth about 1.8 million under the Aminu Trade exception.
Right now, it makes the most sense to waive Leslie before he becomes fully guaranteed, and try to use that TPE to get a player. It's not like you'll miss Travis if you end up filling that spot with a d-leaguer, and you can get a decent 14th man for that 1.8 million.