Quietly show the way to appeal (5)
I believe the answer is:
plead
'way to appeal' is the definition.
(I know that plead is a more specific form of appeal)
'quietly show' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'show' becomes 'lead' (lead can mean to show someone the way).
'p'+'lead'='PLEAD'
'the' acts as a link.
(Other definitions for plead that I've seen before include "Beg or petition" , "Appeal humbly (to)" , "Sue" , "advocate in court" , "Claim; entreat" .)