Quietly go ahead and appeal (5)
I believe the answer is:
plead
'appeal' is the definition.
(I know that plead is a type of appeal)
'quietly go ahead' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'go' becomes 'lead' (synonyms).
'ahead' is a charade indicator (letters next to each other).
'p'+'lead'='PLEAD'
'and' is the link.
(Other definitions for plead that I've seen before include "Argue (for a cause)" , "Supplicate" , "Make an emotional appeal" , "Claim; entreat" , "Argue (a position in court)" .)