That is not a hole, it’s a tightening screw for reservoir bracket… you may be seeing some leakage because someone may have over tightened the screw to the point of puncturing the reservoir. Recommend using correct size Allen wrench to remove screw from bracket and inspect reservoir tank for damage. FYI, brake reservoir works the same so you may want to inspect that one also since the idiot who messed up the clutch probably over tightened the brake one also.
