Covering small area of unproductive land (6)
I believe the answer is:
sheath
'covering' is the definition.
(I know that sheath is a type of covering)
'small area of unproductive land' is the wordplay.
I cannot quite understand how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is found in the answer.
'area' could be 'heath' (heath is a kind of area) and 'heath' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sheath that I've seen before include "jacket" , "Cover for a blade" , "Scabbard" , "(Blade's) cover" , "Cover protecting" .)