Field exposed when fencing is removed (3)
I believe the answer is:
lea
'field' is the definition.
(I've seen this before)
'exposed when fencing is removed' is the wordplay.
'exposed' becomes 'clear' (both can mean unobstructed).
'when fencing is removed' means to look at the middle letters (the letters which fence in the word are removed).
The middle letters of 'clear' are 'LEA'.
(Other definitions for lea that I've seen before include "Poetically, a piece of meadow or pasture" , "authority for teachers" , "Field" , "Tract of pastureland" , "Land growing grass" .)