| CINCHONA | A certainty on a tree, a source of quinine (8) |
| LOGWOODTREE | Central American tree, a source of the dye haematoxylin (7,4) |
| ANCIENTHISTORY | Shattering his certainty on something no longer of importance (7,7) |
| ASSERT | State an absolute certainty on the radio (6) |
| SPINE | Heartwood of a tree; a quill of a hedgehog; a bound edge of a book; a series of vertebrae; or, courage (5) |
| ALKALOID | Any of a class of nitrogenous organic compounds of plant origin that affect human physiology, e.g. morphine, quinine, caffeine etc. (8) |
| DUBONNET | French aperitif; a blend of fortified wine, herbs, spices and quinine (8) |
| INTHEBAG | Coming with us on our travels and that's a certainty (2,3,3) |
| CROWN | Another name for a diadem; the upper part of a hat, cut gem or a tree; a clasping metal cap for a bottle; or, a stag's surroyals collectively (5) |
| PLUCK | A short sharp pull of an eyebrow, fowl's feather or fruit from a tree; a strum or twang of a musical string; or, the heart, liver and lungs of an animal, hence courage, guts, heart or spirit (5) |
| NAILEDON | Constituting a certainty or guaranteed to happen (6,2) |
| CALISAYA | Peruvian shrub or small tree whose bark produces quinine |
| BANKONIT | *"That's a certainty!" |
| MAUVEDYE | First synthetic dye discovered by William Perkins while looking for a method to synthesize quinine (5,3) |
| ACORN | A fruit of a tree, a thing used to make syrup (5) |
| OLEATE | --- of quinine |
| ARCH | Fifty would make it a tree: a thousand, a month (4) |
| EWE | Animal that sounds like a tree, a pronoun, and a letter |
| SAPPHO | Lesbos writer formed by sticky stuff from a tree + a Vietnamese noodle soup |
| ELDER | A tree a bit older than the rest? (5) |
