Crossword Genius

Toy filled with wrong fuel, sadly (9)

Ross

I believe the answer is:

dolefully

'sadly' is the definition.
(in a sad or doleful way)

'toy filled with wrong fuel' is the wordplay.
'toy' becomes 'dolly' (dolly is a kind of toy).
'filled with' is an insertion indicator.
'wrong' is an anagram indicator.
'fuel' with letters rearranged gives 'lefu'.
'dolly' placed around 'lefu' is 'DOLEFULLY'.

I've seen this clue in The Guardian.
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