Remove blockage as old as the hills in one piece (9)
I believe the answer is:
undamaged
'remove blockage as old as the hills in one piece' is the definition.
I can't tell whether this definition defines the answer.
'blockage as old as the hills in one piece' is the wordplay.
I cannot quite see how this works, but
'blockage' could be 'dam' (I've seen this before) and 'dam' is found in the answer.
'old' could be 'aged' (similar in meaning) and 'aged' is found within the answer.
'one' could be 'un' (northern English dialect form of 'one') and 'un' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for undamaged that I've seen before include "Not harmed or injured" , "sound" , "without injuries" .)