Fool could make love in bed (4)
I believe the answer is:
coot
'fool' is the definition.
'love in bed' is the wordplay.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'in' indicates putting letters inside.
'bed' becomes 'cot' (cot is a kind of bed).
'o' going inside 'cot' is 'COOT'.
'could make' acts as a link.
(Other definitions for coot that I've seen before include "Waterbird of rail family" , "Black waterbird" , "Supposedly bald bird" , "'Slow-flying, duck-like bird (4)'" , "Stupid or eccentric man" .)