Take the lead in Moliere's "Tartuffe" (4)
I believe the answer is:
star
'take the lead' is the definition.
(I've seen this in another clue)
'in moliere's tartuffe' is the wordplay.
'in' indicates the answer is hidden within the clue.
'STAR' is hidden within 'molieres tartuffe'.
(Other definitions for star that I've seen before include "- - of Bethlehem" , "Celestial body of hot gases" , "Eg, Rigel, Aldebaran" , "Five-pointed celestial body" , "Heavenly apparition" .)