Dullness small number found in second theatre award (8)
I believe the answer is:
monotony
'dullness' is the definition.
(monotony can mean dullness or tedium)
'small number found in second theatre award' is the wordplay.
'small number' becomes 'no' (abbreviation for 'number').
'found in' is an insertion indicator.
'second' becomes 'mo' (both are short periods of time).
'theatre award' becomes 'Tony' (as in the Tony Awards).
'mo'+'tony'='motony'
'no' inserted inside 'motony' is 'MONOTONY'.
(Other definitions for monotony that I've seen before include "Tediousness" , "It's wearisome" , "Sameness" , "boring routine" , "Unvarying tedium" .)