Familiar chap denounced arrests (10)
I believe the answer is:
accustomed
'familiar' is the definition.
(I've seen this before)
'chap denounced arrests' is the wordplay.
'chap' becomes 'tom' (a man's name).
'denounced' becomes 'accused' (I've seen this in another clue).
'arrests' indicates putting letters inside (inserted letters are held or arrested).
'tom' inserted inside 'accused' is 'ACCUSTOMED'.
(Other definitions for accustomed that I've seen before include "usual" , "Used to" , "familiar" .)