Play 11 challengers (3,6)
I believe the answer is:
the rivals
'play' is the definition.
(I've seen this before)
'11 challengers' is the wordplay.
'tt' becomes 'the' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'challengers' becomes 'rivals' ('rival' can be a synonym of 'challenger').
'the'+'rivals'='THE RIVALS'
Can you help me to learn more?
(Other definitions for the rivals that I've seen before include "Play by Sheridan set in Bath" , "keen competitors" , "a comedy of manners" .)