Usual conqueror destroys article (4)
I believe the answer is:
norm
'usual' is the definition.
(I've seen this in another clue)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for norm that I've seen before include "Rule, standard, pattern" , "Average result" , "Benchmark" , "Small boy" , "Yardstick" .)