1000mm 3 found in car? Blow into this (7)
I believe the answer is:
piccolo
'blow into this' is the definition.
(type of wind instrument)
'1000mm 3 found in car?' is the wordplay.
'1000mm 3' becomes 'i cc' (resembles 1 cc, 1 cubic centimetre).
'found in' means one lot of letters goes inside another.
'car?' becomes 'polo' (I've seen this before).
'icc' placed inside 'polo' is 'PICCOLO'.
(Other definitions for piccolo that I've seen before include "Musical instrument - little (Italian)" , "Smallest of the flute family" , "Shrill woodwind instrument" , "Played, perhaps" , "Small high-pitched flute" .)