Island chain tops geographical lists (11)
I believe the answer is:
archipelago
'island' is the definition.
(thesaurus)
'chain tops geographical lists' is the wordplay.
I cannot quite understand how this works, but
'chain' could be 'ch' (abbreviation for the unit of length) and 'ch' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for archipelago that I've seen before include "Large island group" , "Cluster of islands" , "the Aegean, originally" , "Philippines, say" , "Extensive group of islands" .)