Value sex alone with small rabbit (4,3,4,4)

'value sex alone' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'small rabbit' is the wordplay.
I cannot really see how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is found within the answer.
'rabbit' could be 'buck' (I have seen 'Male rabbit' mean 'buck' so perhaps 'rabbit' could also mean 'buck') and 'buck' is found within the answer.
This explanation may well be incorrect...

'with' is the link.

Can you help me to learn more?