Spectacles carried by Mister Heath (4)
I believe the answer is:
moor
'heath' is the definition.
(both can mean a type of landscape)
'spectacles carried by mister' is the wordplay.
'spectacles' becomes 'oo' (OO resembles a pair of glasses).
'carried by' indicates putting letters inside.
'mister' becomes 'Mr' (synonyms).
'oo' placed into 'mr' is 'MOOR'.
(Other definitions for moor that I've seen before include "Othello, perhaps" , "Tract of uncultivated upland" , "Heath - a North African Muslim" , "Ground that's high" , "Upland tract - eg Othello" .)