Mound of distortion (3)
I believe the answer is:
tor
'mound' is the definition.
(a tor is a rocky mound or hill)
'of distortion' is the wordplay.
'of' says the answer is hidden in the clue.
'TOR' can be found hidden inside 'distortion'.
(Other definitions for tor that I've seen before include "eminence" , "Dartmoor peak" , "rise" , "(Dartmoor) rocky hill" , "Hill or rocky peak" .)