Mother taken in by visitor to Oz offering fruit (6)
I believe the answer is:
tomato
'fruit' is the definition.
(I've seen this before)
'mother taken in by visitor to' is the wordplay.
'mother' becomes 'ma' (ma is a kind of mother).
'taken in by' is an insertion indicator.
'visitor' becomes 'to' (I can't justify this - if you can you should believe this answer much more).
'to'+'to'='toto'
'ma' going inside 'toto' is 'TOMATO'.
'oz offering' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for tomato that I've seen before include "A motto turned out to be fruit/veg" , ""Plum" or "beef" fruit?" , "Shiny red fruit" , "Also called the love apple" , "Type of sauce" .)