Perversely ruin quiet entrance with a crowd (6)
I believe the answer is:
inrush
'entrance with a crowd' is the definition.
I can't judge whether this definition defines the answer.
'perversely ruin quiet' is the wordplay.
'perversely' indicates an anagram.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'ruin' with letters rearranged gives 'inru'.
'inru'+'sh'='INRUSH'
Can you help me to learn more?
(Other definitions for inrush that I've seen before include "Sudden entering flow" , "Sudden flow from outside" , "Sudden move inwards" , "hasty entrance" , "Sudden arrival or entry" .)