Perhaps burglar’s unskilled breaking into short opening passage (8)
I believe the answer is:
intruder
'perhaps burglar's' is the definition.
'unskilled breaking into short opening passage' is the wordplay.
'unskilled' becomes 'rude' (rude can mean basic or unsophisticated).
'breaking into' indicates putting letters inside.
'short' means to remove the last letter.
'opening passage' becomes 'intro' (I've seen this before).
'intro' with its last letter taken away is 'intr'.
'rude' placed into 'intr' is 'INTRUDER'.
(Other definitions for intruder that I've seen before include "Unwelcome guest" , "Housebreaker" , "Uninvited and unwelcome visitor" , "One entering unasked" , "Person who comes in being neither invited nor wanted" .)