Mad cow disease caught by popular dramatist (5)
I believe the answer is:
ibsen
'dramatist' is the definition.
(Ibsen is an example)
'mad cow disease caught by popular' is the wordplay.
'mad cow disease' becomes 'bse' (I've seen this before).
'caught by' is an insertion indicator.
'popular' becomes 'in'.
'bse' placed inside 'in' is 'IBSEN'.
(Other definitions for ibsen that I've seen before include "Norwegian playwright, d. 1906" , "Henrik -, dramatist from fourteen down (Hedda Gabler)" , "'Doll's House' playwright" , "See 7 Down" , "Author of The Master Builder, d. 1906" .)