Importing a mysql database after drop filling up limited / in /tmp deleted file - A problem?
SHOW FULL PROCESSLIST -- there is probably a complex query running, creating a huge tmp table.

Kill that process (go into mysql commandline tool, do SHOW PROCESSLIST to get the pid, then do kill, in the tool, with that number.)

Then scratch your head as to why it is taking so much room.  A likely case:

SELECT ... FROM a, b;


and failing to restrict how a and b should be JOINed.  This is called a CROSS JOIN; it can be huge.