Clog to collapse under pressure (5)
I believe the answer is:
choke
I believe this clue is a double definition.
'clog' is the first definition.
(I know this)
'collapse under pressure' is the second definition.
(I've seen this in another clue)
'to' is the link.
(Other definitions for choke that I've seen before include "Prevent from breathing" , "Become speechless (with emotion)" , "Strangle" , "Have difficulty breathing" , "gag" .)