Fair where one can no longer go? (4)
I believe the answer is:
expo
'fair' is the definition.
(an expo is a type of large exhibition)
'where one can no longer go?' is the wordplay.
'where' indicates anagramming the letters (I've seen this in other clues).
'one' becomes 'a' (a thing is one thing).
'can' becomes 'axe' (terminate).
'no longer' indicates named letters should be taken away.
'go?' becomes 'po' (I am not sure about this - if you are sure you should believe this answer much more).
'axe' with 'a' taken away is 'xe'.
'xe' is an anagram of 'ex'.
'ex'+'po'='EXPO'
(Other definitions for expo that I've seen before include "Public spectacle" , "Public exhibition" , "Public showing" , "Large international exhibition" , "World fair, e.g. Seville 1992" .)