Leave, parking in narrow opening (5)
I believe the answer is:
split
'leave' is the definition.
(thesaurus)
'parking in narrow opening' is the wordplay.
'parking' becomes 'p'.
'in' indicates putting letters inside.
'narrow opening' becomes 'slit' (I've seen this before).
'p' placed into 'slit' is 'SPLIT'.
(Other definitions for split that I've seen before include "Cleave lengthwise" , "Cleave or break up" , "Croatian destination" , "Break in pieces - leave" , "Adriatic port" .)