One who meddles with active group of people (8)
I believe the answer is:
busybody
'one who meddles' is the definition.
(I've seen this before)
'with active group of people' is the wordplay.
'with' says to put letters next to each other.
'active' becomes 'busy' (similar in meaning).
'group of people' becomes 'body' (I've seen this before).
'busy' put next to 'body' is 'BUSYBODY'.
(Other definitions for busybody that I've seen before include "A meddlesome interfering person" , "he'll nose around" , "One minds everyone else's business" , "Person who meddles in the affairs of others" , "Prying person" .)