On the loose (7)
'on the loose' is the definition.
(synonyms)
This is all the clue.
(Other definitions for at large that I've seen before include "Free to roam about, not in confinement" , "in a big way!" , "Glare at, being on the loose" , "Without particular target" , "a wild animal may roam so" .)
(Other definitions for atlarge that I've seen before include "Unrestrained" , "In general" , "as a whole" , "roaming free" .)