cultivated rice field
佃 centers on a cultivated rice field, specifically one worked by a person. The meaning is narrow and concrete: a rice paddy under active cultivation.
佃 combines 亻 (person) and 田 (rice field), suggesting a person working a rice field. The exact historical development is uncertain, but the component relationship is straightforward.
A person 亻 standing beside a rice field 田, tending to the cultivated paddies. 佃 is a rice field under human care.
For テン, imagine ten people working together in the rice field: ten -> テン, and all ten are cultivating the paddies.