Metric measure of capacity (5)
I believe the answer is:
litre
'metric measure of capacity' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for litre that I've seen before include "Amount of liquid" , "Measure of liquid volume" , "It's equal to about 1.75 pints" , "Metric measure of capacity" , "Approx 1 point 75 pints" .)