| THERMOMETER | Term, or theme, adjusted which measures heat |
| THERM | Covering hot period, it measures heat (5) |
| THERMOCOUPLE | It measures heat, more unusually, within hot cupel, possibly |
| THERMOSTATS | The star most unusual in things used to measure heat |
| ANEMOMETERS | Instruments which measure wind speed |
| THREAD | Cordonnet, cotton, crewel, embroidery silk, floss, purl, twist, yarn or other fine long strand of spun fibres; or, a continued idea or theme (6) |
| TOPIC | Subject or theme of a book or speech (5) |
| ESSENCE | Central meaning or theme of a speech or literary work (7) |
| PEDOMETER | Electronic portable device which measures how far a person walks or runs (9) |
| RHEOMETER | Instrument which measures the velocity of blood flow |
| BAROMETER | Instrument which measures pressure (9) |
| TOG | Rating which measures the warmth afforded by quilts. (3) |
| MANOMETER | Instrument which measures the pressure of liquids (9) |
| DITCHMETER | Instrument which measures the fluid flow of liquids (10) |
| GEODIMETER | Brand of surveying instrument which measures distances using a light beam (10) |
| RAINGAUGE | Device which measures precipitation (4,5) |
| ISEQ | Index which measures the performance of the Dublin stock exchange. (4) |
| ODOMETER | Device which measures distance travelled by a wheeled vehicle (8) |
| TIMER | Device which measures duration of a process (5) |
| SPIROMETER | Instrument which measures lung capacity (10) |
