Port possibly built before railway (7)
I believe the answer is:
tilbury
'port' is the definition.
Both the answer and definition are singular nouns.
Maybe they are linked in a way I don't understand?
'possibly built before railway' is the wordplay.
'possibly' indicates anagramming the letters.
'before' means one lot of letters go next to another.
'railway' becomes 'ry' (abbreviation for railway).
'built' is an anagram of '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" .)