Tamper with entrance outside court (6)
I believe the answer is:
doctor
'tamper with' is the definition.
(as in doctoring or manipulating an image)
'entrance outside court' is the wordplay.
'entrance' becomes 'door' (door is a kind of entrance).
'outside' is an insertion indicator.
'court' becomes 'ct' (abbreviation used in road names).
'door' going around 'ct' is 'DOCTOR'.
(Other definitions for doctor that I've seen before include "Medical professional or university don" , "bones" , "An apple a day keeps him away" , "Falsify; quack" , "Health expert" .)