Moors hum strangely producing fungus (8)
I believe the answer is:
mushroom
'fungus' is the definition.
(I know that mushroom is a type of agaric)
'moors hum strangely' is the wordplay.
'strangely' indicates an anagram.
'moors'+'hum'='moorshum'
'moorshum' anagrammed gives 'MUSHROOM'.
'producing' is the link.
(Other definitions for mushroom that I've seen before include "Proliferate" , "develop rapidly" , "Grow very fast" , "Food fungus" , "Common edible fungus" .)