Hostility from scallywag growing (5)
I believe the answer is:
aggro
'hostility' is the definition.
(I've seen this before)
'from scallywag growing' is the wordplay.
'from' says the answer is hidden in the clue.
'AGGRO' is hidden within 'scallywag growing'.
(Other definitions for aggro that I've seen before include "Violence - problems" , "Belligerent trouble" , "Violence - obstructiveness" , "Difficulties, trouble" , "Violent disturbance" .)