One on the pull at Christmas — the Queen? (6)
I believe the answer is:
dasher
This might be a double definition.
'one on the pull at christmas' is the first definition.
(one of the reindeer pulling Santa's sleigh)
'the queen?' is the second definition.
Both the answer and definition are singular nouns.
Maybe there's a link between them I don't understand?
(Other definitions for dasher that I've seen before include "The reindeer that moves very fast" , "Spirited person" , "Haulier" , "Member of team pulling together" , "A sprinter among Santa's reindeer" .)