Which should be used after messing up clustered index? Update statistics, Reindex or Reorganize
You may have misunderstood the way a clustered index works - by definition the data is logically ordered in the sequence of the clustering key, although it's possible for the clustered index to become physically fragmented as page-splits occur when new data is inserted.

If you want to reduce fragmentation either REBUILD or REORGANIZE can be appropriate.
The rule of thumb is to do nothing when fragmentation is below 5%, REORGANIZE when fragmentation is between 5% and 30%, and REBUILD when fragmentation is above 30%.

Index fragmentation is recorded in the DMV sys.dm_db_index_physical_stats. See also the MSDN page on REBUILD/REORGANIZE

It's worth noting that unless you are running SQL Server Enterprise edition, REBUILD cannot be performed on-line - meaning that your table will be inaccessible for the duration of the command. REORGANIZE is always carried out on-line.