Drink with Kelvin in tree (4)
I believe the answer is:
teak
'tree' is the definition.
(I know that teak is a type of tree)
'drink with kelvin' is the wordplay.
'drink' becomes 'tea' (tea is a drink).
'with' is a charade indicator (letters next to each other).
'kelvin' becomes 'K' (abbreviation for the unit of temperature).
'tea'+'k'='TEAK'
'in' acts as a link.
(Other definitions for teak that I've seen before include "Hard durable wood" , "Hardwood found naturally in the Far East" , "Hard strong wood" , "Take away with very hard wood" , "Hardwood tree" .)