Let out group without charge (3,4)
I believe the answer is:
set free
'let out' is the definition.
('set free' can be a synonym of 'let out')
'group without charge' is the wordplay.
'group' becomes 'set' (set is a kind of group).
'without charge' becomes 'free' (I've seen this before).
'set'+'free'='SET FREE'
(Other definitions for set free that I've seen before include "Release, remove restraints" , "without the box" , "Clear" , "Released" , "no longer detained" .)