Need gear to move rat (8)
I believe the answer is:
renegade
'rat' is the definition.
(thesaurus)
'need gear to move' is the wordplay.
'to move' indicates anagramming the letters.
'need'+'gear'='needgear'
'needgear' is an anagram of 'RENEGADE'.
(Other definitions for renegade that I've seen before include "Betrayer, deserter" , "Perfidious" , "Treacherous deserter" , "A deserter from a cause or faith" , "Rebel, outlaw" .)