Liberate one soul in torment (7)
I believe the answer is:
unloose
'liberate' is the definition.
(synonyms)
'one soul in torment' is the wordplay.
'in torment' is an anagram indicator (I've seen this in other clues).
'one'+'soul'='onesoul'
'onesoul' is an anagram of 'UNLOOSE'.
(Other definitions for unloose that I've seen before include "Let free" , "Set free" , "Release" .)