Stop supporting a group with no backing (7)
I believe the answer is:
abandon
'stop' is the definition.
(I've seen this before)
'supporting a group with no backing' is the wordplay.
'supporting' is a charade indicator (letters next to each other) (in a down clue, some letters go under others).
'group' becomes 'band' (band can mean a group of people).
'with' says to put letters next to each other.
'backing' shows that the letters should be reversed in order.
'no' backwards is 'on'.
'a' put next to 'band' is 'aband'.
'aband'+'on'='ABANDON'
(Other definitions for abandon that I've seen before include "Completely give up; desert" , "dump" , "Cast aside" , "Leave high and dry" , "scrap" .)