Fiddle in plant (5)
I believe the answer is:
viola
I believe this clue is a double definition.
'fiddle' is the first definition.
(thesaurus)
'plant' is the second definition.
(viola is a kind of plant)
'in' acts as a link.
(Other definitions for viola that I've seen before include "Flower -- stringed instrument" , "Bowed string instrument" , "String instrument of a range between the violin and cello" , "Shakespeare heroine; instrument" , "Cesario when in drag" .)