| BARLEYCORN | Obsolete unit of length equal to one third of an inch |
| BARLEY | -corn; unit of length equal to one third of an inch (6) |
| FOOT | Unit of length equal to one third of a yard (4) |
| ELL | An obsolete unit of length equal to approximately 45 inches |
| LIGHTYEAR | Unit of distance roughly equal to one third of a parsec |
| INCH | Unit of imperial length equal to one twelfth of a foot or 2.54 cm; one quarter of a hand; or, a unit of measurement for pressure in a barometer (4) |
| KILDERKIN | An obsolete unit of liquid capacity equal to 16 or 18 Imperial gallons |
| LEAGUE | An obsolete unit of distance, commonly equal to three miles (6) |
| RIGHT | Any of four species of stout-bodied whales having an enormous head measuring one-quarter to one-third their total body length. (Also, opposite of left.) (5) |
| EXPOUND | Give an interpretation of obsolete unit of weight? (7) |
| CABLE | Collection of wires twisted or bonded as a rope; the chain of a ship's anchor; or, a unit of length equal to one tenth of a nautical mile (5) |
| ANGSTROM | Unit of length equal to one tenth of a nanometre, chiefly used to express wavelengths of electromagnetic radiation (8) |
| OUT | One-third of an inning, to a pitcher |
| NOBLE | Obsolete coin worth one third of an old pound |
| TOUCAN | With a colourful bill measuring up to one-third of its body length, a tropical fruit-eating bird found high in the rainforest canopy (6) |
| LIBREVILLE | West African capital city, home to one third of the country's population (10) |
| MM | A metric unit of length equal to one thousandth of a meter. |
| CM | A metric unit of length equal to one hundredth of a meter. |
| MICRON | A unit of length equal to one millionth of a meter (6) |
| NANOMETRE | Unit of length equal to one billionth of a metre (9) |
