One saying too much, a bumbler? Both, oddly (12)
I believe the answer is:
blabbermouth
'one saying too much' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'a bumbler? both oddly' is the wordplay.
'oddly' indicates an anagram (letters in an odd order).
'a'+'bumbler'+'both'='abumblerboth'
'abumblerboth' is an anagram of 'BLABBERMOUTH'.
Can you help me to learn more?
(Other definitions for blabbermouth that I've seen before include "Indiscreet talker" , "One who talks too much" , "Secret revealer" , "Telltale" , "Indiscreet individual - humbler abbot (anag)" .)