Posh folk gradually changing sides (6)
I believe the answer is:
gentry
'posh folk' is the definition.
'gentry' can be an answer for 'folk' (thesaurus). I am not sure about the 'posh' bit.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for gentry that I've seen before include "who are noble" , "People of social rank just below nobility" , "They're next below the nobility in position and birth" , "cream?" , "Privileged class" .)