Quietly start to pray (5)
I believe the answer is:
plead
'to pray' is the definition.
(I've seen this in another clue)
'quietly start' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'start' becomes 'lead' (I can't explain this - if you can you should give a lot more credence to this answer).
'p'+'lead'='PLEAD'
Can you help me to learn more?
(Other definitions for plead that I've seen before include "Beg, implore" , "advocate in court" , "Supplicate" , "Argue (for a cause)" , "Implore, entreat" .)