Off-the-wall effect? (4)
I believe the answer is:
echo
'off-the-wall effect?' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for echo that I've seen before include "Nymph (only able to repeat the last words of others)" , "Reflected sound" , "Before foxtrot" , "Be suggestive of" , "What evokes memories" .)