Look after extremely rowdy room of children (7)
I believe the answer is:
nursery
'room of children' is the definition.
'look after extremely rowdy' is the wordplay.
'look after' becomes 'nurse' (I've seen this before).
'extremely' says to hollow out the word (remove centre letters).
'rowdy' with its middle removed is 'ry'.
'nurse'+'ry'='NURSERY'
(Other definitions for nursery that I've seen before include "place for promising growth?" , "Race for horses that are two" , "Growing environment for plants or children" , "where small fry are found" , "Place where young plants are grown" .)