fill in, fill up, make good
塡 centers on filling a void or deficiency: adding material to fill up a hole, completing something, or making good on a shortfall.
塡 combines 土 (earth) with 眞, which likely contributes the sound and the idea of filling or making full. The character is a variant of 填, where the right side is the simplified 真.
The left side is earth 土, and the right side 眞 looks like a container being packed full. Picture shoveling earth into a hole until it is completely filled and made good.
For テン, imagine filling a hole with ten shovelfuls of earth: ten -> テン, and the earth fills the gap completely.