Polish star's point of no return (7)
I believe the answer is:
rubicon
'point of no return' is the definition.
(as in the phrase 'crossing the Rubicon')
'polish star's' is the wordplay.
'polish' becomes 'rub' (polish meaning rub to make shiny).
'star' becomes 'icon'.
'rub'+'icon'='RUBICON'
(Other definitions for rubicon that I've seen before include "Cross it to pass the point of no return" , "Caeser crossed this river in a decisive step- no going back" , "No, I curb the fateful river" , "River crossed by Caesar in decisive move" , "term used in 12 [PIQUET]" .)