Viz advice for caravan owner (2,3)
I believe the answer is:
to wit
'caravan owner' is the definition.
I know nothing about this answer so I can't judge whether this works.
'viz advice for' is the wordplay.
I cannot really see how this works, but
'for' could be 'to' (eg both can mean 'in the opinion of') and 'to' is found within the answer.
The remaining letters 'wit' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for to wit that I've seen before include "what to do with a broken-down car!" , "i.e." , "That is to say" , "In other words" , "specifically" .)