In this case we want to get the average of values but we also want to ignore certain values, say if when the deviceType column is greater than 0 and not a negative number. The mysql engine will ignore null values so we can accomplish this using a case statement or MySQLs build in if function
select sum(clicks) as clicks, AVG(IF(deviceType > 0 deviceType, NULL)) as 'AvgDevicesGreaterThanZero', term from clickData group by term