let somebody/something loose
US /lɛt ˈsʌmˌbɑːdi ˈsʌmˌθɪŋ luːs/
UK /lɛt ˈsʌmˌbɑːdi ˈsʌmˌθɪŋ luːs/

1.
soltar, dar rédea solta a
to allow a person or animal to be free, or to allow something to be used or to happen without control
:
•
The zookeepers decided to let the animals loose in the larger enclosure.
Os tratadores do zoológico decidiram soltar os animais no recinto maior.
•
Once he gets a microphone, he just lets himself loose and talks for hours.
Assim que ele pega um microfone, ele simplesmente se solta e fala por horas.