Reacting to a new wave the Queen's introduced (9)
I believe the answer is:
answering
'reacting to' is the definition.
'a new wave the queen's introduced' is the wordplay.
'a new' becomes 'an' (I've seen this in other clues).
'wave' becomes 'swing'.
'the queen' becomes 'er' (Elizabeth Regina).
'introduced' means one lot of letters goes inside another.
'swing' enclosing 'er' is 'swering'.
'an'+'swering'='ANSWERING'
(Other definitions for answering that I've seen before include "Picking up receiver" , "Responding" , "Replying" , "Acknowledging" .)