Horrify a quiet friend (5)

I believe the answer is:

appal

'horrify' is the definition.
(I know that horrify can be written as appal)

'a quiet friend' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'friend' becomes 'pal' (pal can mean a friend).
'a'+'p'+'pal'='APPAL'

(Other definitions for appal that I've seen before include "Greatly horrify" , "Fill with horror" , "To shock, dismay" , "exhibiting dismay" , "Greatly dismay" .)

I've seen this clue in The Daily Express and The Independent.

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