loosen

loosen /ˈluːsn̩/ verb
loosens; loosened; loosening
loosen
/ˈluːsn̩/
verb
loosens; loosened; loosening
Britannica Dictionary definition of LOOSEN
1 
a  [+ object] : to make (something) less tight or firm : to make (something) loose or looser
— sometimes used figuratively
b  [no object] : to become less tight or firm : to become loose or looser
2 
: to become or to cause (something) to become less strict
[+ object]
[no object]

loosen someone's tongue

: to cause someone to talk more freely : to cause someone to say things that would not usually be said

loosen up

[phrasal verb]
1 
: to make or become less tense : relax
2 
loosen (someone or something) up or loosen up (someone or something) : to cause (someone or something) to relax