Greetings from the sandbank.  I've found this one very difficult but managed to fill the grid with the requisite number of blanks.  Could I test my understanding before trying the next stage?
I have six clues where the extra word has only one letter which differs from the answer.  These six letters from an anagram of the surname of a film director: his first name is that of the surname of a  famous male star.  
Am I on the right lines?  If so I'll splash on.  If not I'll go and have a herring and regroup tomorrow.  
Many thanks.  This forum is really helpful in isolated rural lockdown