Pressure in narrow opening causes rupture (5)
I believe the answer is:
split
'rupture' is the definition.
(thesaurus)
'pressure in narrow opening' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'in' indicates putting letters inside.
'narrow opening' becomes 'slit' (I've seen this in another clue).
'p' inserted within 'slit' is 'SPLIT'.
'causes' acts as a link.
(Other definitions for split that I've seen before include "Diverge" , "Divided" , "Ripped" , "Go separate ways" , "Left" .)