Don having a bit of fun during January (4)
I believe the answer is:
juan
'don' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see a link between them that I can't see?
'a bit of fun during january' is the wordplay.
'a bit of fun' becomes 'u' (I can't explain this - if you can you should give a lot more credence to this answer).
'during' means one lot of letters goes inside another.
'january' becomes 'Jan' (synonyms).
'u' inserted inside 'jan' is 'JUAN'.
'having' is the link.
Can you help me to learn more?
(Other definitions for juan that I've seen before include "Don . . . . Was a famous lover" , "Don . . . . was a great lover" , "--les-Pins, Fr. resort" , "Don . . . . was a notorious Spanish womaniser" , "Don ...., legendary seducer" .)