Playwright provides this quiet sentimental expression (4)
I believe the answer is:
shaw
'playwright' is the definition.
(George Bernard Shaw)
'this quiet sentimental expression' is the wordplay.
'this quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'sentimental expression' becomes 'aw' (I can't justify this - if you can you should believe this answer much more).
'sh'+'aw'='SHAW'
'provides' acts as a link.
Can you help me to learn more?
(Other definitions for shaw that I've seen before include "G. B. ---; T. E. ---" , "Irish author" , "George Bernard -, Irish dramatist" , "Thicket; playwright" , "making an appearance in Craiglockhart?" .)