Possible Clues:

• Fake reporting of school tests by heads of English and religion
• Substitute bitter vetch at first sign of zoogonidia
• Simulated tears shed by Zulu leader
• Tears shed before Tevez finally makes substitute
• 'Gunners' at Zaragoza producing substitute
• Queen occupied throne, perhaps a variable substitute
• Cheap substitute
• Like chicory vis-à-vis coffee
• Plastic, so to speak
• Can't be real turnabout for last letter arriving at end of week