There you are in France, picking up one instrument (5)
I believe the answer is:
viola
'instrument' is the definition.
(viola is a kind of instrument)
'there you are in france picking up one' is the wordplay.
I cannot quite see how this works, but
'are' could be 'a' (the 'are' is a metric unit of area) and 'a' is located in the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
The remaining letters 'vol' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Other definitions for viola that I've seen before include "Shakespearean character" , "Large violin" , "String instrument of a range between the violin and cello" , "Large fiddle" , "Pansy-like flower" .)