If you presumed that employee may elope after getting full salary, is really a matter to every establishment and they have to do something to stop it. You can not put a clause because would goes against act & rules. A letter can be issued stating that due to pandemic situation some of your payments are deferred as happened to all other employees in our establishment, your balance amount will be cleared in later date once situation improves. You pay the basic withholding other components but do not stop payment.