Mushrooms may be amusing, man! (6)
I believe the answer is:
fungus
'mushrooms may' is the definition.
The definition and answer can be both plants as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'amusing man' is the wordplay.
'amusing' becomes 'fun' (synonyms).
'man' becomes 'gus' ().
'fun'+'gus'='FUNGUS'
'be' acts as a link.
Can you help me to learn more?
(Other definitions for fungus that I've seen before include "Kind of plant, mushroom, toadstool etc" , "'Mushroom or toadstool, say (6)'" , "Organism such as a mushroom" , "Mould or similar growth" , "A mushroom, toadstool or mould" .)