Waterlogged turf beside lair (6)
I believe the answer is:
sodden
'waterlogged' is the definition.
(I've seen this before)
'turf beside lair' is the wordplay.
'turf' becomes 'sod' (both can mean a piece of grass).
'beside' is a charade indicator (letters next to each other) (I've seen this in other clues).
'lair' becomes 'den' (synonyms).
'sod'+'den'='SODDEN'
(Other definitions for sodden that I've seen before include "Completely saturated" , "heavy with moisture" , "'Soaked, sopping (6)'" , "Made very wet" , "Totally saturated" .)