Raised pressure does change the arrangement (5)
I believe the answer is:
posed
'raised pressure does change the arrangement' is the definition.
I can't judge whether this definition defines the answer.
'raised pressure does change' is the wordplay.
'raised pressure' becomes 'p' (scientific abbreviation. I am not sure about the 'raised' bit.).
'change' indicates anagramming the letters.
'does' is an anagram of 'osed'.
'p'+'osed'='POSED'
Can you help me to learn more?
(Other definitions for posed that I've seen before include "Presented (a question)" , "Positioned" , "Struck attitude, perhaps for painter" , "Arranged for pictorial purposes" , "Faced the camera" .)