The upright part of a Christmas tree (4)
I believe the answer is:
mast
'the upright part' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'of a christmas tree' is the wordplay.
'of' indicates a hidden word.
'MAST' is hidden in the letters of 'christmas tree'.
Can you help me to learn more?
(Other definitions for mast that I've seen before include "Main vertical spar of vessel" , "Pole aboard; fruit for pigs" , "Sail carrier" , "Upright transmitter; fruit of oak trees" , "Long vertical pole" .)