Possible Clues:

• Central region
• ''There's a spy in our ___!''
• In the middle half mistimed first delivery included
• Inner location
• Where one is surrounded by other things
• In our ___ (among us)
• "In the ___ of This" (Expatriate)
• Thick? Way beyond stupid, on reflection!
• Centre of activity
• Isabel Allende's "In the __ of Winter"