I guess straight forward enough question, what would be the resultant chemical if Cs2Se + Sc = ?
You did not say if this reaction should be in air, or any specified solvent. The conditions could make a difference. Scandium is a metal, probably a solid (not sure); Cs2Se, what state of matter? Is it dissolved in something? My unrefined guess would be to check in a table of electrode potentials to look for a reasonable redox reaction. Maybe a true inorganic chemist would read your question and give an expert answer.