Polish child almost flipped over puzzle setter (5)
I believe the answer is:
rubik
'puzzle setter' is the definition.
(Erno Rubik, inventor of the Rubik's cube)
'polish child almost flipped over' is the wordplay.
'polish' becomes 'rub' (polish meaning rub to make shiny).
'child' becomes 'kid' (synonyms).
'almost' means to remove the last letter (most of the word but not all of it).
'flipped over' says the letters should be written in reverse.
'kid' with its last letter taken away is 'ki'.
'ki' in reverse letter order is 'ik'.
'rub'+'ik'='RUBIK'
(Other definitions for rubik that I've seen before include "Inventor of a famous cube" , "The cube man" , "Puzzle cube inventor" .)