Related Clues:

• Open space between two things, mind it
• The doctor around a space that's open
• In a doctor there might be a hiatus like this
• When something goes, that's what it leaves
• The family doctor has a space in him
• A GP might have nothing in him
• Longtime mall chain
• Narrow space
• Space between peaks
• Trendy clothing giant
• See 15
• Space (maybe for a year?)
• Orthodontist's diagnosis, sometimes
• Generation separator
• Reason for braces, perhaps