Queen following formal introduction (6)
I believe the answer is:
primer
'introduction' is the definition.
(I've seen this before)
'queen following formal' is the wordplay.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'following' means one lot of letters go next to another.
'formal' becomes 'prim' (I've seen this in other clues).
'er' after 'prim' is 'PRIMER'.
(Other definitions for primer that I've seen before include "it might be used by one 7 [PAINTING]" , "Introductory textbook or first coat of paint" , "Basic teaching book" , "Educational book" , "He charges" .)