There is so much wrong or misleading information in this thread. If you don't know something for certain, please don't post.
Offering copyright advice that you're not sure of is incredibly dangerous and could easily cost someone their channel and/ or a lot of money.
As for the original question, outside of changing the music to something you actually have permissions to use, there is no way 'to get around it.'
It doesn't matter if it's the full song, 30 seconds or even one second. If you don't have the needed permissions, you are in violation.
If you upload a 20 second music clip, expect Content ID (an automated copyright matching process) to find and match the music as soon as your video is uploaded. From there, whoever owns the rights on the song will likely monetize the video on their behalf, collect all future earnings the video may make, and possibly block it from playing in certain countries. Luckily, you won't receive a copyright strike and will likely even have the option to remove or change the offending audio.
So long as you don't mind them monetizing and receiving all income generated from ads on your video, there isn't any issue- but there is no way to 'get around' it.