Cool prison venues to be redesigned (12)
I believe the answer is:
unresponsive
'cool' is the definition.
(thesaurus)
'prison venues to be redesigned' is the wordplay.
'to be redesigned' indicates an anagram.
'prison'+'venues'='prisonvenues'
'prisonvenues' anagrammed gives 'UNRESPONSIVE'.
(Other definitions for unresponsive that I've seen before include "disengaged" , "Not reacting to stimuli" , "Not answering" .)