quid pro quo

a quid pro quo —ты мне, я тебе
something that you do for someone or give to someone when they have agreed to do something for you
This is a Latin phrase which means 'something for something'.

The government's commitment to release political prisoners is a quid pro quo for the suspension of armed struggle by the rebels.

See also [баш на баш]
[you scratch my back, i'll scratch yours]