Plonker from Stanislavski's school (4)
I believe the answer is:
kiss
'plonker' is the definition.
(you might plonk a kiss on someone)
'from stanislavski's school' is the wordplay.
'from' indicates the answer is hidden within the clue.
'KISS' can be found hidden inside 'stanislavskis school'.
(Other definitions for kiss that I've seen before include "Cross" , "x (that may be French)" , "Embrace" , "Amorous greeting" , "Act of love" .)