Lake in front of dry den (4)
I believe the answer is:
lair
'den' is the definition.
('lair' can be a synonym of 'den')
'lake in front of dry' is the wordplay.
'lake' becomes 'l'.
'in front of' says to put letters next to each other.
'dry' becomes 'air' (airing is a kind of drying).
'l'+'air'='LAIR'
(Other definitions for lair that I've seen before include "Wild animal's place of refuge" , "office?" , "Rail about wild animal's home" , "Supposed large ape, the Bigfoot" , "Place to hide" .)