Starbucks Corp. tried to dig itself out of controversy Monday by attempting to clarify a policy toward nonpaying guests that generated an onslaught of weekend criticism.

The Seattle-based retailer on Saturday had said it would allow all guests in its U.S. company-owned stores to use its cafes, including its restrooms, whether or not they make a purchase. That announcement, which attracted some support, also drew complaints that cafes wouldn’t have enough seats for paying customers and would turn into homeless shelters and...