place in Xinjiang province
闐 is a rare kanji used primarily as a place name in Xinjiang province. Its standalone meaning is unclear beyond that geographic reference.
闐 combines 門 (gate) with 真, but the historical origin and the role of 真 in this character are uncertain. It may have been created as a phono-semantic compound for a place name, but the exact development is unclear.
The gate 門 surrounds 真, like a true gate marking the entrance to a place in Xinjiang. Think of it as the gate to the true location.
For テン, picture ten gates leading to the place in Xinjiang: ten -> テン, and each gate has the true inner mark.