Initially master has spoken in lesson (5)
I believe the answer is:
moral
'lesson' is the definition.
('moral' can be a synonym of 'lesson')
'initially master has spoken' is the wordplay.
'initially' indicates taking the first letters.
'has' says to put letters next to each other.
'spoken' becomes 'oral' ('oral' can be similar in meaning to 'spoken').
The initial letter of 'master' is 'm'.
'm'+'oral'='MORAL'
'in' is the link.
(Other definitions for moral that I've seen before include "Underlying significance of a story or event" , "Virtuous and principled" , "ethical principle" , "Honourable" , "knowing right from wrong" .)