Future fern or fungus (5)
I believe the answer is:
spore
I believe this is a double definition.
'future fern' is the first definition.
(I've seen this in another clue)
'fungus' is the second definition.
(thesaurus)
(Other definitions for spore that I've seen before include "Asexual reproductive body" , "Tiny reproductive cell of fungus or fern" , "Ropes (anag.)" , "Fungus reproducer" , "Reproductive body produced by fungi" .)