Shoo flies away regularly in dungeon (4)
I believe the answer is:
hole
'dungeon' is the definition.
(I've seen this in another clue)
'shoo flies away regularly' is the wordplay.
'away regularly' indicates alternate letters (letters taken away at regular intervals).
'shoo'+'flies'='shooflies'
The alternating letters of 'shooflies' are 'HOLE'.
'in' acts as a link.
(Other definitions for hole that I've seen before include "Predicament - golfer's target" , "mess" , "Gap; difficult situation" , "Aperture; cavity" , "This in one is a golfer's dream!" .)