Apply pressure to central problem (3)
I believe the answer is:
rub
'problem' is the definition.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for rub that I've seen before include "Ay, there's the - (Hamlet)" , "Cause friction" , "Polish - difficulty" , "Irritate-...the wrong way" , "Apply friction to - difficulty" .)