error: invalid type argument of ‘unary *’ (have ‘int’)

Since c is holding the address of an integer pointer, its type should be int**:

int **c;
c = &a;

The entire program becomes:

#include <stdio.h>                                                              
int main(){
    int b=10;
    int *a;
    a=&b;
    int **c;
    c=&a;
    printf("%d",(**c));   //successfully prints 10
    return 0;
}

Barebones C program to produce the above error:

#include <iostream>
using namespace std;
int main(){
    char *p;
    *p = 'c';

    cout << *p[0];  
    //error: invalid type argument of `unary *'
    //peeking too deeply into p, that's a paddlin.

    cout << **p;    
    //error: invalid type argument of `unary *'
    //peeking too deeply into p, you better believe that's a paddlin.
}

ELI5:

The master puts a shiny round stone inside a small box and gives it to a student. The master says: "Open the box and remove the stone". The student does so.

Then the master says: "Now open the stone and remove the stone". The student said: "I can't open a stone".

The student was then enlightened.