One tucked into mature spirit in crude container? (3,4)
I believe the answer is:
oil drum
'crude container?' is the definition.
(container for crude oil)
'one tucked into mature spirit' is the wordplay.
'one' becomes 'i' (Roman numeral).
'tucked into' indicates putting letters inside.
'mature' becomes 'old' (associated in meaning).
'spirit' becomes 'rum' (alcoholic spirit).
'i' placed within 'old' is 'oild'.
'oild'+'rum'='OIL-DRUM'
'in' acts as a link.
(Other definitions for oil drum that I've seen before include "Large container" , "Container for crude" , "Fuel container" , "Metal barrel for fuel" .)