Instrument for mixing oil in French wine? (6)
I believe the answer is:
violin
'instrument' is the definition.
(musical instrument)
'mixing oil in french wine?' is the wordplay.
'mixing' indicates an anagram.
'in' means one lot of letters goes inside another.
'french wine?' becomes 'vin' ('wine' in French).
'oil' is an anagram of 'iol'.
'iol' put within 'vin' is 'VIOLIN'.
'for' acts as a link.
(Other definitions for violin that I've seen before include "A stringed musical instrument, say a Stradivarius" , "It'a played with a bow" , "An elevated fiddle" , "Instrument with four strings" , "Nigel Kennedy instrument" .)