Macabre hairy relative practisin’ sex in bed (6,3)

'macabre hairy relative' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'practisin' sex in bed' is the wordplay.
'practisin'' becomes 'usin' (I can't explain this - if you can you should give a lot more credence to this answer).
'sex' becomes 'it' (a common euphemism).
'in' indicates putting letters inside.
'bed' becomes 'cot' (cot is a type of bed).
'usin'+'it'='usinit'
'usinit' put into 'cot' is 'COUSIN ITT'.

Can you help me to learn more?