It's stiff for both master and pupil (6)
I believe the answer is:
formal
'it's stiff' is the definition.
(similar in meaning)
'for both master and pupil' is the wordplay.
'both master' becomes 'ma' (Master of Arts. I am not sure about the 'both' bit.).
'and' is a charade indicator (letters next to each other).
'pupil' becomes 'L' (as in L-plates for a learner driver).
'for'+'ma'+'l'='FORMAL'
Can you help me to learn more?
(Other definitions for formal that I've seen before include "Conforming to accepted rules, as of dress" , "Ceremonious or official" , "Conventional - ceremonious" , "It's required by rule" , "Not casual" .)