Seaside railway? (9)
I believe the answer is:
coastline
'seaside railway?' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'seaside railway?' is the wordplay.
'seaside' becomes 'coast' (I've seen this before).
'railway?' becomes 'line' (line is a kind of railway).
'coast'+'line'='COASTLINE'
Can you help me to learn more?
(Other definitions for coastline that I've seen before include "Outline of land from sea" , "Where the sea meets the shore" , "Shore boundary" , "Seaboard" , "Shape of the seashore" .)