Fence door (4)
I believe the answer is:
gate
'fence door' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for gate that I've seen before include "Kind of door as in wall or fence" , "Confine to college" , "Narrow opening" , "Hinged barrier in an entrance" , "Spectators - entrance" .)