From prison, dash to the open ground (8)
I believe the answer is:
dartmoor
'from prison' is the definition.
I can't judge whether this defines the answer.
'dash to the open ground' is the wordplay.
'dash' becomes 'd'art' (synonyms).
'to the open ground' becomes 'moor' (I've seen this before).
'dart'+'moor'='DARTMOOR'
Can you help me to learn more?
(Other definitions for dartmoor that I've seen before include "Famous English prison in Devon" , "Devon pony breed" , "National Park in Devon" , "with ponies?" , "West Country prison" .)