That of the crowd at the New Den? (4)
I believe the answer is:
roar
'den?' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for roar that I've seen before include "Deep loud sound as of lion or bull" , "Yell" , "Shout loudly" , "Cry (as a lion)" , "24 [BOOM]" .)