Sostener (en. Hold)

/sos.te'neɾ/

Slang Meanings

To keep it secret.
Don't tell anyone, we have to keep it under wraps.
No se lo digas a nadie, hay que sostenerlo.
To support someone in a risky adventure or situation.
I'm going to back you in this plan, but only if you have a good argument.
Voy a sostenerte en este plan, pero solo si tienes un buen argumento.