Russian spirit very old duke and king admired, initially (5)
I believe the answer is:
vodka
'russian spirit' is the definition.
(I've seen this before)
'very old duke and king admired initially' is the wordplay.
'very' becomes 'v' (abbreviation).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'duke' becomes 'd'.
'and' means one lot of letters go next to another.
'initially' says to take the initial letters.
The first letters of 'king admired' is 'ka'.
'v'+'o'+'d'+'ka'='VODKA'
(Other definitions for vodka that I've seen before include "Colourless alcoholic spirit associated with Russia" , "Spirit made from rye, wheat or potatoes" , "Colourless liquor" , "Russian alcoholic drink" , "shot?" .)