Clue: Sulks in pub? The opposite – it's high point for Walter (6)
Answer: PINNET
Explanation: Definition: high point for Walter 
**INN** ("pub") *in* **PET** ("sulk"), *so the sulk's not in the pub, but* "the opposite". 
*A "pinnet" is a word used by Wlater Scott for a pinnacle (ie a "high point")