Speaker's educated and stiff (4)
I believe the answer is:
taut
'stiff' is the definition.
(I've seen this in another clue)
'speaker's educated' is the wordplay.
'speaker's' indicates a 'sounds like' (homophone) clue.
'educated' becomes 'taught' (similar in meaning).
'taught' is a homophone of 'TAUT'.
'and' is the link.
(Other definitions for taut that I've seen before include "On the slope" , "Tense, stretched tight" , "Pulled or drawn tight" , "Tightly drawn" , "Without slack" .)