Many a yarn has been spun on these islands (6)
I believe the answer is:
canary
'these islands' is the definition.
The definition suggests an adverb but the answer is not.
'many a yarn has been spun' is the wordplay.
'many' becomes 'c' (C is the Roman numeral for y00).
'yarn' becomes 'y' (this might be a standard abbreviation I've not previously seen).
'has' is a charade indicator (letters next to each other).
'been' becomes 'ran' (running is a kind of being).
'spun' shows that the letters should be reversed in order.
'y'+'ran'='yran'
'yran' written backwards gives 'nary'.
'c'+'a'+'nary'='CANARY'
'on' is the link.
Can you help me to learn more?
(Other definitions for canary that I've seen before include "grass" , "This flies" , "Yellow bird, formerly taken down mines" , "a sort of finch" , "Finch prized for its song" .)