### Clue: It's Rocky, ordering at least four pints (6)
### Answer: QUARTZ 
 ### Explanation: Definition: It's Rocky

Homophone [*ordering*] of **QUARTS** ("at least four pints")
 

 
I'm not entirely convinced by "ordering" as a homophone indicator, but I suppose it could be stretched to "asking for out loud" such as in a bar.