Port possibly built before railway (7)
I believe the answer is:
tilbury
'port' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I don't see?
'possibly built before railway' is the wordplay.
'possibly' indicates an anagram.
'before' means one lot of letters go next to another.
'railway' becomes 'ry' (abbreviation).
'built' with letters rearranged gives 'tilbu'.
'tilbu'+'ry'='TILBURY'
Can you help me to learn more?
(Other definitions for tilbury that I've seen before include "Carriage; Thames port" , "Thames container port" .)