Clue: Books satellite in space, understanding stupid nit's purpose (9)
Answer: INTENTION
Explanation: Definition: purpose

**NT** (New Testament, so "books") +** IO** ("satellite") *in* **EN** (printer's "space") *understanding* (i.e. standing under) ***(nit) **[anag:*stupid*], so **INT-E(NT-IO)N**
 
*Io is the third largest moon of Jupiter.