Finn knees car drunkenly: it's a gift! (12)
I believe the answer is:
frankincense
'a gift' is the definition.
(gift given to the baby Jesus)
'finn knees car drunkenly' is the wordplay.
'drunkenly' is an anagram indicator.
'finn'+'knees'+'car'='finnkneescar'
'finnkneescar' with letters rearranged gives 'FRANKINCENSE'.
'it's' acts as a link.
(Other definitions for frankincense that I've seen before include "Nativity gift; aromatic tree resin" , "One of three wise men's gifts" , "Gum resin used as incense" , "present at birth" , "Aromatic gum resin - an original Christmas present!" .)