When we create a clustered index does it takes extra space?

I am asking this question with repect to mysql database.I read that clustered index orders the table based on primary key or columns that we provide for making clustered index, where as in non clustered index there is separate space taken for key and record pointer.

Also I read as there is no separate index table, clustered index is faster than non clustered index where as non clustered index must first look into index table find corresponding record pointer and fetch record data

Does that mean there is no extra space taken for clustered index?

PS:I know that there are already some similar answers on this question but I can't understand.

There is no extra space taken because every InnoDB table is stored as the clustered index. There is in fact only the clustered index, and secondary indexes. There's no separate storage for data, because all the unindexed columns are simply stored in the terminal nodes of the clustered index. You might like to read more about it here: https://dev.mysql.com/doc/refman/8.0/en/innodb-index-types.html

It is true that if you do a lookup using a secondary index, and then select columns besides those in the secondary index, InnoDB would do a sort of double lookup. Once to search the secondary index, which results in the value of the primary key(s) where the value you are searching for is found, and then it uses those primary keys to search the clustered index to combine with the other columns.

This double-lookup is mitigated partially by the Adaptive Hash, which is a cache of frequently-searched values. This cache is populated automatically as you run queries. So over time, if you run queries for the same values over again, it isn't so costly.