Clue: Chief ought to tumble before anything else (5,2,3)
Answer: FIRST OF ALL
Explanation: Chief ought to tumble before anything else (5,2,3)
Think there's an error here as there is no indication of the O. 
I can see **FIRST** ("chief") and **FAL**L ("tumble").
 
The clue would work if it read "Conifers to tumble before anything else" (FIRS TO FALL)