Speaker uttered almost drivel on reflection (6)
I believe the answer is:
orator
'speaker' is the definition.
(orator is a kind of speaker)
'uttered almost drivel on reflection' is the wordplay.
'uttered' becomes 'oral' (both can mean spoken).
'almost' means to remove the last letter (most of the word but not all of it).
'drivel' becomes 'rot' (rot is a kind of drivel).
'on reflection' is a reversal indicator.
'rot' reversed gives 'tor'.
'oral' with its final letter removed is 'ora'.
'ora'+'tor'='ORATOR'
(Other definitions for orator that I've seen before include "he can talk" , "Eloquent public speaker" , "He addresses" , "I declaim" , "Eloquent type" .)