Type of fruit, one in apple (5)

I believe the answer is:

galia

'type of fruit' is the definition.
(I know that Galia is a type of muskmelon)

'one in apple' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'apple' becomes 'gala' (I've seen this before).
'i' placed into 'gala' is 'GALIA'.

I've seen this clue in The Guardian.

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