Universal wit entertains son (6)
I believe the answer is:
cosmic
'universal' is the definition.
(relating to the universe)
'wit entertains son' is the wordplay.
I cannot quite understand how this works, but
'son' could be 's' (genealogical abbreviation for son) and 's' is found in the answer.
The remaining letters 'comic' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for cosmic that I've seen before include "Enormous" , "Huge" , "Large -- universal" , "Of the universe, infinite" , "Originating in outer space" .)