Somewhere far away protester has messed up (12)
I believe the answer is:
stratosphere
'somewhere far away' is the definition.
(the stratosphere is high up in the sky)
'protester has messed up' is the wordplay.
'messed up' indicates anagramming the letters.
'protester'+'has'='protesterhas'
'protesterhas' with letters rearranged gives 'STRATOSPHERE'.
(Other definitions for stratosphere that I've seen before include "Layer of high air around the earth" , "Layer above the earth where temperature generally increases with height" , "Atmospheric layer" , "High level above earth" , "Area containing ozone layer" .)