Waiting for table level lock - Info says NULL> What could be causing this lock?

This is from one of our Slave servers in a master-slave replication setup. What could be causing the locak mentioned in the 2nd line? Under info it shows only NULL. And it does not have anymore info other than the Id.

I think because of this the slave is lagging too far behind the master.

mysql> show processlist ;
+---------+--------------+---------------------+--------------+---------+---------+----------------------------------+------------------------------------------------------------------------------------------------------+
| Id      | User         | Host                | db           | Command | Time    | State                            | Info                                                                                                 |
+---------+--------------+---------------------+--------------+---------+---------+----------------------------------+------------------------------------------------------------------------------------------------------+
|   12877 | system user  |                     | NULL         | Connect | 4548125 | Waiting for master to send event | NULL                                                                                                 |
|   12878 | system user  |                     | NULL         | Connect |   11413 | Waiting for table level lock     | NULL                                                                                                 |
| 1776357 | my_live_wh01 | 10.100.50.146:35496 | my_live_wh01 | Sleep   |    2038 |                                  | NULL 

mysql Ver 14.14 Distrib 5.6.20 on RHEL 6.4