Histrionic works with involuntary response (8)
I believe the answer is:
operatic
'histrionic' is the definition.
(I've seen this before)
'works with involuntary response' is the wordplay.
'works' becomes 'opera' ('opera' is an alternative plural of 'opus').
'with' means one lot of letters go next to another.
'involuntary response' becomes 'tic' (I've seen this before).
'opera'+'tic'='OPERATIC'
(Other definitions for operatic that I've seen before include "Macbeth is" , "description of Lulu?" , "as in G&S?" , "Irate cop (anag)" , "like Wagner's Ring" .)