Across:
   8. Some mathematics fortified innate lunacy (15)
   9. Some sort of fools spiral out of control (6)
  10. Irons stimulate - stimulate back! (8)
  11. Optimists... panned out badly with these (15)
  12. Chaotic results if knocked back, as due to be contracted (7)
  13. Variety of characters from the Bard (7)
  16. Rum initiation as cleverly working with area's limitation (15)
  18. Jug of wine, as esteemed gift (8)
  19. To Nigeria, another foreigner (6)
  20. Special train late only in crossing borders (15)
Down:
   1. Filipino miscast - bad stereotyping! (15)
   2. Fair arrangement dismisses Chad's children for instance (8)
   3. Tupi's oppression - bad stereotyping! (15)
   4. Erroneous costing for seeking divine knowledge (7)
   5. Rum initiation as cleverly working with area's limitation (15)
   6. Ernest, travelling writer (6)
   7. Program layout compliant with PC procedure (15)
  14. They feel for stake Anne lost (8)
  15. Slap ten around, then nine, now eight (7)
  17. Cans of beer, as esteemed gift (6)