Time in metal box (3)
I believe the answer is:
tin
'box' is the definition.
(I've seen this in other clues)
'time in metal' is the wordplay.
'time in' becomes 't' (abbreviation. I am not sure about the 'in' bit.).
'metal' becomes 'In' (In is an example).
't'+'in'='TIN'
Can you help me to learn more?
(Other definitions for tin that I've seen before include "With copper, makes bronze" , "Kind of metal often used as food container" , "Silver-white element often used in food containers" , "Earnings" , "Atomic number 50" .)