Came down again in a certain capacity (5)
I believe the answer is:
litre
'a certain capacity' is the definition.
'litre' can be an answer for 'capacity' (I've seen this before). I am not sure about the 'a certain' bit.
'came down again' is the wordplay.
'came down' becomes 'lit' (light or alight can mean to land).
'again' becomes 're' (prefix meaning 'again').
'lit'+'re'='LITRE'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for litre that I've seen before include "Fluid measure" , "Metric measure of capacity" , "Unit of liquid measure" , "Amount of liquid" , "quantity of drink" .)