How to delete mgmt_acld.out ?

Hi guys I need your help !

/var/tmp/mgmt_acld.out has so big volume so, I want to delete that

I tried cat /dev/null > mgmt_acld.out but this file still has huge volume ( just delete for seconds )

so, How to delete that ?

please let me know if you know way !

ps. [ 154302460 Dec 20 23:50 mgmt_acld.out]

thank you