First on the list of Christmas presents (9)
I believe the answer is:
partridge
'list of christmas presents' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'first on the' is the wordplay.
I cannot quite see how this works, but
'first' could be 'i' (Roman numeral for one or first) and 'i' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for partridge that I've seen before include "Widespread bird" , "Game bird (in a pear tree?)" , "Peculiarly apt girder for the game bird" , "Flighty type" , "early Christmas present" .)