This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
訵 combines 言 (speech) with 四 (four), but the historical origin and original meaning are uncertain. It may have been a phono-semantic compound, but the exact development is unclear.
With 言 (speech) and 四 (four), imagine four people whispering secretly, trying to find out information. This fits the idea of spying or inquiring covertly.
For チ, imagine a spy whispering 'chee' as a secret code while gathering information: chee -> チ.