Fan of grass cuckoo nest that’s covered round river (6)
I believe the answer is:
stoner
'fan of grass' is the definition.
I can't judge whether this defines the answer.
'cuckoo nest that's covered round river' is the wordplay.
'cuckoo' is an anagram indicator (I've seen this in other clues).
'that's covered' is an insertion indicator.
'round' becomes 'o' (o is a circular letter).
'river' becomes 'r' (abbreviation for river).
'nest' with letters rearranged gives 'stne'.
'stne' going around 'o' is 'stone'.
'stone'+'r'='STONER'
Can you help me to learn more?
(Other definitions for stoner that I've seen before include "No rest (anag) - cannabis user" , "Slang for habitual smoker of cannabis" , "Slang for habitual pot-smoker" .)