King Charles fenced grassland plain (5)
I believe the answer is:
clear
'plain' is the definition.
(synonyms)
'king charles fenced grassland' is the wordplay.
I cannot really see how this works, but
'king' could be 'lear' (Shakespeare's King Lear) and 'lear' is present in the answer.
A single letter 'c' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for clear that I've seen before include "Transparent - free of obstruction" , "Set free of charges" , "Bold" , "Open; not cloudy" , "Jump over without contact" .)