Starts to turn ravaging, without intervention dropping to upsetting (9)
I believe the answer is:
traumatic
'starts to' is the definition.
I can't tell whether this defines the answer.
'turn ravaging without intervention dropping to upsetting' is the wordplay.
'turn ravaging' becomes 'tr' (this might be a standard abbreviation of which I'm unaware).
'without intervention' becomes 'automatic' (automatic means happening without intervention).
'dropping' suggests deleting specific letters.
'upsetting' says the letters should be written in reverse.
'to' written backwards gives 'ot'.
'automatic' with 'ot' taken away is 'aumatic'.
'tr'+'aumatic'='TRAUMATIC'
(Other definitions for traumatic that I've seen before include "Deeply disturbing" , "Direly shocking" , "Emotionally shocking" , "Deeply distressing" , "Psychologically damaging" .)