Cut in demand over time hurt (9)
I believe the answer is:
detriment
'hurt' is the definition.
(I know that hurt can be written as detriment)
'cut in demand over time' is the wordplay.
'cut' becomes 'trim' (trim is a kind of cut).
'in' is an insertion indicator.
'demand' becomes 'need' (synonyms).
'over' is a reversal indicator.
'time' becomes 't' (abbreviation).
'need' written backwards gives 'deen'.
'trim' put within 'deen' is 'detrimen'.
'detrimen'+'t'='DETRIMENT'
(Other definitions for detriment that I've seen before include "Harm, damage" , "State of being harmed or damaged" , "Possible loss" , "hurt" , "Damage, loss" .)