Dull waterway's beginning to be upgraded? (5)
I believe the answer is:
banal
'dull waterway's' is the definition.
'banal' can be an answer for 'dull' (I've seen this before). I am not sure about the 'waterway's' bit.
'beginning to be upgraded?' is the wordplay.
'beginning to' says to take the initial letters.
'upgraded?' becomes 'anal' (I am not sure about this - if you are sure you should believe this answer much more).
The initial letter of 'be' is 'b'.
'b'+'anal'='BANAL'
Can you help me to learn more?
(Other definitions for banal that I've seen before include "Overfamiliar through overuse" , "flat" , "Uninspiring" , "Uninteresting, commonplace" , "Tediously commonplace" .)