let in on
US /let ɪn ɑːn/
UK /let ɪn ɑːn/

1.
memberi tahu, membiarkan tahu
to allow someone to share a secret or to know something that is not known by many people
:
•
They finally let me in on their plans for the surprise party.
Mereka akhirnya membiarkan saya tahu rencana mereka untuk pesta kejutan.
•
She refused to let him in on the secret.
Dia menolak untuk membiarkan dia tahu rahasianya.