Quiet English lady (3)
I believe the answer is:
she
'lady' is the definition.
(I've seen this before)
'quiet english' is the wordplay.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'english' becomes 'e' (abbreviation).
'sh'+'e'='SHE'
(Other definitions for she that I've seen before include "Female pronoun" , "H. Rider Haggard novel" , "1887 Rider Haggard novel" , "way to refer to mare" , "Book" .)