The definition of back-scratching refers to an exchange of favors.
When you promise to help someone get a job and he, in turn, promises he will hire you once he is in charge, this is an example of back-scratching.
Informal a reciprocal exchange of favors, aid, or compliments
Origin of back-scratching; from the saying, “You scratch my back; I'll scratch yours”
- Present participle of backscratch.