Theme: DUCK-LING fling. Five common English words that can serve double duty as either nouns or verbs are adorned with a diminutive LING suffix, yielding another common English language noun, now in an off-beat, humorous diminutive form. Some of them are still verbs, as well.
17A. Very narrow fissure? : CRACKLING. N: 1) As per the clue, 2) A bit of fried pork or goose fat; V: producing a series of snapping noises.
26A. Landfill in a toy city? : DUMPLING. N: 1) As per the clue, 2) A lump of dough cooked in liquid.
38. Minuscule tattoo? : INKLING. N: 1) As per the clue, 2) A hint, 3) A vague notion, 4) (plural) An Oxford University literary discussion group whose members included C.S. Lewis and J.R.R. Tolkien; V: Communicating in an undertone or whisper (obsolete.)
40A. Dollhouse dress adornment? : BOWLING. N: 1) Tiny BOW, as per the clue, 2) A game in which one knocks down wooden objects with a rolled ball. V: Playing that game.
49A. Where to wear a training bra? : BUSTLING. N: Per the clue, A, AA, or AAA miniscule bosom. (Dare I?) V: Moving energetically.
62A. Very young hobo? : TRAMPLING. N: Son of ON THE ROAD, perhaps. V: Treading in a heavy-footed, damaging manner
And the unifier, 67A. Waterfowl whose young inspired this puzzle's theme : DUCKS. Baby DUCKS are DUCKLINGS.
Wow! Six theme entries, plus a unifier, and very complex wordplay, with layered double, and sometimes triple meanings, a rich musical sub-theme, and a bit of DF. I am AGAPE, but will not DUCK out on you. Lets DUCK INTO the puzzle and see what we can find.
1. Birthday secret : WISH. We make our wishes known. Otherwise, you get what you get.
5. "Back in Black" band : ACDC. Of all the bands that (tried to ) sound like Led Zeppelin, I preferred Led Zeppelin.
14. __ Domini : ANNO. Latin: In the year of Our Lord.
15. Bodybuilder's supplement : WHEY. Dairy-based protein source.
16. Hand-dyeing craft : BATIK.
19. Vintage violin : AMATI
20. Michael Moore health-care film : SICKO. Unavoidably political, ergo: no comment.
21. Melody : TUNE. We opened the Jazz Fest with this TUNE. Hardest Big Band Chart I've ever played. I have a video posted on Facebook. If you're on and interested, send me an email, and I'll send you a link.
23. Rock 'n' roll middle name : ARON. Alvis ARON Presley
24. Didn't sell : KEPT.
28. CIA part: Abbr. : AGCY. Central intelligence AGENCY.
30. Arthur Fiedler et al. : MAESTRI. Pl. of MEASTRO - orchestra conductors.
48. Did a farrier's job : SHOD. Installed horseshoes. A farrier is a specialist in equine hoof care, including the
trimming and balancing of horses' hooves and the placing of shoes on
their hooves. Now you know.
52. Lacking spice : TAME
54. Chain selling stacks : IHOP. International House of Pancakes