Clue: Statute said to protect India's principal river (5)
Answer: LOIRE
Explanation: Definition: river

The best I can do for this clue is:
 
Homophone of **LAW** ("statute") [*said*] *to protect* **I**(ndia) [*'s principal*]
 
*If that is what the setter had in mind, I'm not convinced – LAW and LORE are not homophones, at least not where I come from.