Briefly need hot drink and litre of milk (7)
I believe the answer is:
lacteal
'of milk' is the definition.
(lacteal means relating to milk)
'briefly need hot drink and litre' is the wordplay.
'briefly' means to remove the last letter.
'need' becomes 'lack' (to lack something is to be in need of it).
'hot drink' becomes 'tea' (I've seen this before).
'and' means one lot of letters go next to another.
'litre' becomes 'L' (abbreviation).
'lack' with its final letter removed is 'lac'.
'lac'+'tea'+'l'='LACTEAL'
(Other definitions for lacteal that I've seen before include "Milky resin" , "Milk-like; pertaining to milk" .)