By the sound of it, worked in education, far from relaxed (4)
I believe the answer is:
taut
'far from relaxed' is the definition.
'by the sound of it worked in education' is the wordplay.
'by the sound of it' shows a homophone (sound like).
'worked in education' becomes 'taught'.
'taught' is a homophone of 'TAUT'.
(Other definitions for taut that I've seen before include "Tightly drawn" , "On the slope" , "Without slack" , "Held in tension" , "seaworthy" .)