Near bridge, crossing island in sea (7)
I believe the answer is:
caspian
'sea' is the definition.
Both the answer and definition are singular nouns.
Maybe there's an association between them I don't understand?
'near bridge crossing island' is the wordplay.
'near' becomes 'ca' (I am not sure about this - if you are sure you should believe this answer much more).
'bridge' becomes 'span' (synonyms).
'crossing' indicates putting letters inside (to cross can mean to go over or around).
'island' becomes 'i' (geographical abbreviation).
'span' enclosing 'i' is 'spian'.
'ca'+'spian'='CASPIAN'
'in' is the link.
Can you help me to learn more?
(Other definitions for caspian that I've seen before include "Prince --, Narnia book" , "World's largest inland sea" , "-- Sea, inland lake" .)