Clue: Cockerel made man nervous at first (5)
Answer: CAPON
Explanation: Definition: Cockerel
A charade of CAPO ('made man' – a Mafia reference; although I think that they are not quite equivalent, a CAPO is – presumably – a 'made man', committed to the Mafia to the extent of murder, but not necessarily vice versa. Which is good enough for the clue) plus N ('**N**ervous at first'). Of course, the cock-a-doodle-don't.