Where camper might be initially irritating 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 initially irritating on' is the wordplay.
'where camper might be' becomes 'in tent' (someone might camp in a tent).
'initially' says to take the initial letters.
The first letter of 'irritating' is 'i'.
'intent'+'i'+'on'='INTENTION'
(Other definitions for intention that I've seen before include "Aim, purpose" , "Design" , "end" , "Plan, purpose" , "goal" .)