| PROTONS | Particles composed of two up quarks and one down quark |
| PION | Composed of one up quark and one down antiquark, the lightest meson and a component of cosmic raays (4) |
| PROTON | Two up quarks and a down quark |
| NEUTRON | It contains an up quark and two down quarks |
| MESON | Subatomic particle composed of one quark and one antiquark |
| HADRONS | Particles composed of quarks |
| MESONS | Particles composed of a quark and an antiquark |
| CURDCHEESE | Doctor screeched about first sign of up quark, perhaps |
| KNIGHT | 'Green' BR steam locomotive 75029 moves two across and one down, or one across and two down! (6) |
| KIP | 1,000lb; a monetary unit of Laos; a wooden paddle to spin Australian pennies in a game of two-up; a calf/lambskin; a bundle of hides; a bed; or, a nap or a snooze (3) |
| THUMB | One of two up for approval (5) |
| KICK | Hides of calves or lambs; catnaps, dozes or snoozes; beds or lodgings; or, paddles for spinning pennies in the Australian game of two-up (4) |
| COIN | Currency item needed for the Australian game of two-up |
| SWY | Game of two-up (Aus. slang) |
| SPINNER | Who tosses the coins in a game of two-up (7) |
| CEDAR | Start to round odd members of 2 up for representative of Lebanon? |
| IRONED | Pressed one right and one down (6) |
| GELLMANN | Nobel Prize-winning physicist who proposed the concept of strangeness in quarks and contributed towards the classification of elementary particles (4-4) |
| ANAGLYPH | What is a picture composed of two images, one in red and one in green, so as to appear stereoscopic? (8) |
| SNP | Contributing to our fundamental understanding of the universe, the "truth" quark and most massive of all known elementary particles (3) |
