Forbidden to have native sides in group (6)
I believe the answer is:
banned
'forbidden' is the definition.
(banning is a kind of forbidding)
'native sides in group' is the wordplay.
'sides' says to hollow out the word (remove centre letters) (only the letters on the sides are used).
'in' indicates putting letters inside.
'group' becomes 'band' (band can mean a group of people).
'native' with its middle taken out is 'ne'.
'ne' put inside 'band' is 'BANNED'.
'to have' acts as a link.
(Other definitions for banned that I've seen before include "expelled" , "Group on radio" , "Taboo" , "Censored" , "Outlawed" .)