One celibate woman beds fellow as a joke (2,3)
I believe the answer is:
in fun
'as a joke' is the definition.
(I've seen this before)
'one celibate woman beds fellow' is the wordplay.
I cannot quite see how this works, but
'one' could be 'un' (northern English dialect form of 'one') and 'un' is found in the answer.
'woman' could be 'f' (I've seen this in other clues) and 'f' is found in the answer.
The remaining letters 'in' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for in fun that I've seen before include "As a joke - not seriously" , "for a laugh" , "Not intended seriously" , "to raise a smile?" .)