It's heard to good effect if raised on greeting (2-2)
I believe the answer is:
hi-fi
'it's heard to good effect' is the definition.
I can't judge whether this definition defines the answer.
'if raised on greeting' is the wordplay.
'raised' shows that the letters should be reversed in order (going up in a down clue).
'on' means one lot of letters go next to another.
'greeting' becomes 'hi' (hi is a kind of greeting).
'if' written backwards gives 'fi'.
'fi' after 'hi' is 'HI-FI'.
Can you help me to learn more?
(Other definitions for hi-fi that I've seen before include "Good quality sound system, in short" , "Stereo" , "High fidelity" , "Good sound reproduction, in short" , "Audio equipment" .)