Wet turf above animal’s lair (6)
I believe the answer is:
sodden
'wet' is the definition.
(similar in meaning)
'turf above animal's lair' is the wordplay.
'turf' becomes 'sod' (both can mean a piece of grass).
'above' means one lot of letters go next to another (in a down clue, some letters go above others).
'animal's lair' becomes 'den' (I've seen this before).
'sod'+'den'='SODDEN'
(Other definitions for sodden that I've seen before include "Muddy" , "Made very wet" , "Drenched, really soaked" , "Thoroughly wet, soaked" , "heavy with moisture" .)