Reverberation from karate-chop (4)
I believe the answer is:
echo
'reverberation' is the definition.
(synonyms)
'from karate-chop' is the wordplay.
'from' indicates a hidden word.
'ECHO' can be found hidden inside 'karate chop'.
(Other definitions for echo that I've seen before include "What evokes memories" , "repetitive" , "Marked by heat" , "Reflection of sound - Greek nymph" , "Radio operator's word for 'E'" .)