Terrarium plant (4)
I believe the answer is:
fern
'terrarium plant' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for fern that I've seen before include "Flowerless plant with feathery fronds" , "Feathery frondy plant" , "Bracken, for example" , "Tracheophyte plant" , "Plant producing spores" .)