Moderate South Africa group holding power (7)
I believe the answer is:
sparing
'moderate' is the definition.
(thesaurus)
'south africa group holding power' is the wordplay.
'south africa' becomes 'SA' (abbreviation).
'group' becomes 'ring' (a ring is a criminal organisation).
'holding' means one lot of letters goes inside another.
'power' becomes 'p' (symbol in physics).
'sa'+'ring'='saring'
'saring' enclosing 'p' is 'SPARING'.
(Other definitions for sparing that I've seen before include "Scanty - merciful" , "Economic (with resources)" , "Economical; having mercy" , "Moderate, economical" , "Thrifty" .)