Monotony of new diet, uniform beginning and end (6)
I believe the answer is:
tedium
'monotony' is the definition.
(I've seen this before)
'new diet uniform beginning and end' is the wordplay.
'new' indicates anagramming the letters.
'beginning and end' says to hollow out the word (remove centre letters).
'uniform' with its middle taken out is 'um'.
'diet' anagrammed gives 'tedi'.
'tedi'+'um'='TEDIUM'
'of' acts as a link.
(Other definitions for tedium that I've seen before include "Boredom with monotony" , "State of being bored" , "Banality" , "Boredom or dullness" , "Routine" .)