Quiet little chap, this crony? (3)
I believe the answer is:
pal
'crony?' is the definition.
('pal' can be a synonym of 'crony')
'quiet little chap' is the wordplay.
'quiet' becomes 'pp' (music symbol for 'pianissimo').
'little' means to remove the last letter (the word is not quite complete).
'chap' becomes 'al' (man's name).
'pp' with its last letter removed is 'p'.
'p'+'al'='PAL'
'this' acts as a link.
(Other definitions for pal that I've seen before include "Close friend" , "Mate, buddy" , "Friend (colloq.)" , "Bud" , "Buddy, chum" .)