jmc

Note that $a-2=0$, since $a=2$. Thus the product in question is $$(a-10)\cdots (a-3)\cdot (a-2)\cdot (a-1)\cdot a=(a-10)\cdots (a-3)\cdot 0\cdot (a-1)\cdot a,$$ which is $\boxed{0}$, since zero times any real number is zero.