Clue: So unhappy to have just missed podium, not seen as superior looking ahead (10)
Answer: HENCEFORTH
Explanation: Definition: looking ahead
Parsed this as: HENCE="So", FO[**U**]RTH="just missed podium", without/"not" the **U**=upper class, as opposed to 'non-U'="seen as superior"… which means "unhappy" is redundant? 
Or perhaps "not seen as superior" is an instruction to remove the first letter of "unhappy" from FOURTH?