Would-be barber on the rampage — all hide! (7)
I believe the answer is:
delilah
'would-be barber' is the definition.
(Delilah had Samson's hair cut in the Bible)
'on the rampage all hide' is the wordplay.
'on the rampage' indicates anagramming the letters.
'all'+'hide'='allhide'
'allhide' anagrammed gives 'DELILAH'.
(Other definitions for delilah that I've seen before include "She sheared Samson" , "Samson's femme fatale" , "Dangerous temptress - Samson's girlfriend" , "Judges woman" , "Samson's treacherous girl friend" .)