Liberate secure complex (6)
I believe the answer is:
rescue
'liberate' is the definition.
(thesaurus)
'secure complex' is the wordplay.
'complex' indicates anagramming the letters.
'secure' is an anagram of 'RESCUE'.
(Other definitions for rescue that I've seen before include "Secure (anag) - release" , "Save someone from a dangerous situation" , "Free - recovery" , "Pull from danger" , "Salvage" .)