Punish group breaking into places to the north (6,2)

'punish' is the definition.
(to string someone up is to hang them)

'group breaking into places to the north' is the wordplay.
'group' becomes 'ring' (a ring is a criminal organisation).
'breaking into' indicates putting letters inside.
'places' becomes 'puts' ('put' can be a synonym of 'place').
'to the north' shows that the letters should be reversed in order (in a down clue, letters go up or 'northward').
'puts' reversed gives 'stup'.
'ring' inserted into 'stup' is 'STRING UP'.