Bedevilled groups spend oddly (9)
I believe the answer is:
possessed
'bedevilled' is the definition.
'groups spend oddly' is the wordplay.
'groups' becomes 'posses'.
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
The alternate letters of 'spend' are 'sed'.
'posses'+'sed'='POSSESSED'
(Other definitions for possessed that I've seen before include "It's collected" , "Had ownership of" , "being under a spell" , "Bore" , "Enjoyed" .)