So he prefers a zip -- sensible chap (2,5,2,3)
I believe the answer is:
no flies on him
'so' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'he prefers a zip sensible chap' is the wordplay.
I cannot really see how this works, but
'he' could be 'son' and 'son' is found in the answer.
'chap' could be 'hi' and 'hi' is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for no flies on him that I've seen before include "Sensible fellow!" , "He doesn't hang about!" , "So he has a zip?" .)