Pressure on Polish hero worried deep thinker (11)
I believe the answer is:
philosopher
'deep thinker' is the definition.
(someone who thinks about deep topics)
'pressure on polish hero worried' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'on' means one lot of letters goes inside another.
'worried' is an anagram indicator.
'polish'+'hero'='polishhero'
'polishhero' anagrammed gives 'philosoher'.
'p' put into 'philosoher' is 'PHILOSOPHER'.
(Other definitions for philosopher that I've seen before include "Profound thinker" , "Investigator of the nature of being" , "Deep thinker" , "Immanuel Kant, for example" , "Metaphysician" .)