Hear about very mature Othello, say (7)
I believe the answer is:
tragedy
'othello say' is the definition.
(I know that Othello is a tragedy)
'hear about very mature' is the wordplay.
'hear' becomes 'try' (to hear or try a case in the legal sense).
'about' means one lot of letters goes inside another.
'very mature' becomes 'aged' (elderly).
'try' placed around 'aged' is 'TRAGEDY'.
(Other definitions for tragedy that I've seen before include "Dire misfortune" , "Serious catastrophe" , "King Lear, perhaps" , "Serious type of play" , "Terribly sad thing" .)