Where camper might be if leaving loudly on purpose (9)
I believe the answer is:
intention
'purpose' is the definition.
(I know that purpose can be written as intention)
'where camper might be if leaving loudly on' is the wordplay.
'where camper might be' becomes 'in tent' (someone might camp in a tent).
'leaving' suggests deleting specific letters.
'loudly' becomes 'f' (short for forte - 'loud' in music).
'if' with 'f' taken out is 'i'.
'intent'+'i'+'on'='INTENTION'
(Other definitions for intention that I've seen before include "Plan, purpose" , "Aim, objective" , "Aim, plan" , "end" , "Aim, purpose" .)