you are trying to delete 4 parameters(policy name, sourec, destination addres and application) in one line. try the below
#edit security policies from-zone untrust to-zone trust
# del policy cloud-access
and if you dont have any other polices between untrust to trust you need run below
#delete security policies from-zone untrust to-zone trust
#edit security policies from-zone untrust to-zone trust
# del policy cloud-access
and if you dont have any other polices between untrust to trust you need run below
#delete security policies from-zone untrust to-zone trust