Behave with affection or audacity (4)
I believe the answer is:
neck
'audacity' is the definition.
(neck can mean rudeness or audacity)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for neck that I've seen before include "Narrow connecting part - smooch" , "and what is at the bottom of it" , "Part of body connecting head and torso" , "It's risky to stick it out" , "A hard one shows some nerve" .)