Friend's initial anger about gross Christmas gift (12)
I believe the answer is:
frankincense
'christmas gift' is the definition.
(gift given to Jesus)
'friend's initial anger' is the wordplay.
'friend's initial' becomes 'frank' (I am not sure about this - if you are sure you should believe this answer much more).
'anger' becomes 'incense' (to incense is make angry).
'frank'+'incense'='FRANKINCENSE'
'about gross' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for frankincense that I've seen before include "Christmas gift" , "Source of pleasant scent" , "Gum resin used as incense" , "One of three wise men's gifts" , "Aromatic gum resin - an original Christmas present!" .)