Single theatrical award shows lack of diversity (8)
I believe the answer is:
monotony
'lack of diversity' is the definition.
(monotony means sameness or a lack of variety)
'single theatrical award' is the wordplay.
'single' becomes 'mono' (prefix meaning single).
'theatrical award' becomes 'tony' (Tony Awards).
'mono'+'tony'='MONOTONY'
'shows' acts as a link.
(Other definitions for monotony that I've seen before include "fixed routine" , "Tedious lack of variety" , "Unvarying tedium" , "Tediousness" , "boring routine" .)