### Clue: Norma for instance lifted endless marijuana over time (5)
### Answer: OPERA 
 ### Explanation: Definition: Norma for instance
 **Reversal of**(lifted) [ "pot"(slang for marijuana) **minus its last letter** (endless …) ] **placed above**(over, in a down clue) ERA(a long period of time).
Answer: An example of which;for instance is Norma by Vincenzo Bellini.