Q:

Function to remove all the entries of specific duplicate number in the list

How to delete all the entries of specific number from list.
However the way i followed below is just removing one time
newList = [1,2,3,4,5,2,6,7,5,8]
for num in newList:
    if newList.count(num) > 1:
        newList.remove(num)
print(newList)

Result
[1, 3, 4, 2, 6, 7, 5, 8]

A:

There's 2 issues with your code:

you're modifying the list while iterating it. So you miss the next number (the "3" and the 2nd "2")
help(list.remove) explicitly says it'll "remove first occurrence of value" 

With a couple of print in your code, this becomes obvious:
newList = [1,2,3,4,5,2,6,7,5,8]
for num in newList:
    print (num)
    if newList.count(num) > 1:
        print('   -->removing')
        newList.remove(num)
print(newList)

outputs: 
1
2
   -->removing
4
5
   -->removing
6
7
5
8

