He'll go to bed with you, but his involvement is strictly financial (8,7)
I believe the answer is:
sleeping partner
'he'll go to bed with you but his involvement is strictly financial' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he'll go to bed with you but his involvement' is the wordplay.
I cannot really understand how this works, but
'go' could be 'ping' (pinging is a kind of going) and 'ping' is found in the answer.
'involvement' could be 'part' (part is a kind of involvement) and 'part' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sleeping partner that I've seen before include "silent in company?" , "One not known" , "A capital provider" , "Inactive business associate" .)