Unshaven king gets stuck into booze (8)
I believe the answer is:
whiskery
'unshaven' is the definition.
('whiskery' can be similar in meaning to 'unshaven')
'gets stuck into booze' is the wordplay.
'gets stuck' becomes 'er' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'into' means one lot of letters goes inside another.
'booze' becomes 'whisky' (whisky is a kind of booze).
'er' going into 'whisky' is 'WHISKERY'.
'king' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for whiskery that I've seen before include "mutton chops" , "With facial hair" , "Hairy" , "Bearded" .)