Crossword Genius

Friends upset over wicked-sounding guitar technique (4,4)

Ross

I believe the answer is:

slap bass

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'wicked-sounding guitar technique' is the definition.
I know nothing about this answer so I cannot judge whether this works.

'friends upset over' is the wordplay.
'friends' becomes 'pals' (pal is a kind of friend).
'upset' is a reversal indicator.
'over' becomes 'bass' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pals' in reverse letter order is 'slap'.
'slap'+'bass'='SLAP BASS'

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I've seen this clue in The Times.
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