If my previous post OID does not work, try this OIDs to get memory of Clearpass.
memTotalSwap .1.3.6.1.4.1.2021.4.3
DESCRIPTION "The total amount of swap space configured for this host."
memAvailSwap .1.3.6.1.4.1.2021.4.4
DESCRIPTION "The amount of swap space currently unused or available."
memTotalReal .1.3.6.1.4.1.2021.4.5
DESCRIPTION "The total amount of real/physical memory installed
on this host."
memAvailReal .1.3.6.1.4.1.2021.4.6
DESCRIPTION "The amount of real/physical memory currently unused
or available."
memBuffer .1.3.6.1.4.1.2021.4.14
DESCRIPTION "The total amount of real or virtual memory currently
allocated for use as memory buffers.
memCached .1.3.6.1.4.1.2021.4.15
DESCRIPTION "The total amount of real or virtual memory currently
allocated for use as cached memory.