When you are someone's "beck and call," you follow with his orders. You remain slavishly attentive to all of the person's requirements in an effort to make him happy. Your order is to fulfil the person's wish.

The young prince was at his wife's beck and call.

There are a few reporters we know who are at the minister's beck and call.

The word "beck" is essentially an abbreviated version of the verb "to call." Typically, a "beck" is a silent gesture that you offer to someone to get their attention. A simple head nod or finger motion could be used as the signal.

Who are the people who are very attentive to the movements of a person's hands and head? Naturally, servants! The old days saw servants at the beck and call of their master. Using either "calling" or "beckoning," a master could persuade a servant to carry out his orders.