Across:
   1. Cravings may be part of your gestation (5)
   4. Mother issue? Of course she's gonna help build the wall! (5)
   7. Some new music for an old man (3)
   9. Number taken to tango? (3)
  10. see 6 down
  11. Serious end of cake after first slice (5)
  12. Mr Greene's return meant leaving out a number of students (9)
  13. Medicine making you sick? (6)
  14. Give courage to Mr Kelly to throw me back (8)
  16. Singapore noodles almost mild (3)
  17. Broad affectedness of retro comic: "I'm Edna, possums!" (8)
  19. Serious end of cake after first slice (6)
  22. It breaks up passages between cecum and splenic flexure perhaps? (9)
  24. Mocked leaders of junta as poorly educated dictators (5)
  26. For breathing freely, try air pores (11)
  27,4dn. Possible source of 19 11 26 5 10 9 we celebrate during Vietnamese new year (3 6)
  28. Famous fullback is so small! (3)
  29. Like opportunity to make declaration in test? (5)
  30. Stain and dry it out (5)
Down:
   1. Zealous follower among faithful travellers? (5)
   2. Perhaps some airborne sputum you expel finally into the world (7)
   3. Cite verse about keeping mum (9)
   4. see 27 across
   5. Bad omens: dry set of symptoms (8)
   6,10ac. Pathogen seen in various corn (5 11)
   7. Cape Herald? (7)
   8. It's often used to make stories beyond exciting (4 5)
  13. Shots that might get developed for infection risks (9)
  14. Essentially fleeced the Europe that Britain joined (1 1 1)
  15. Being exceedingly happy drove Joey insane (9)
  16. Primarily, makes promotions involving terrible lies? (8)
  18. Great enemy lurking within? Quarantine me, sister! (7)
  20. Provide agency to measure captured soldier and queen (7)
  21. Ring immersed in mucus by finally turning nose up (6)
  23. Who wants to build belt and road with broken chain? (5)
  25. Some crooned it (typically) (5)