Christmas show gets Henry married, in spirit (7)
I believe the answer is:
phantom
'spirit' is the definition.
(phantom is a kind of spirit)
'christmas show gets henry married' is the wordplay.
'christmas show' becomes 'panto' (short for pantomime - traditional Christmas show).
'gets' is an insertion indicator (gets can mean captures or absorbs).
'henry' becomes 'H' (symbol for the unit of electrical inductance).
'married' becomes 'm' (abbreviation, e.g. in genealogy).
'panto' going around 'h' is 'phanto'.
'phanto'+'m'='PHANTOM'
'in' acts as a link.
(Other definitions for phantom that I've seen before include "Apparition, spectre" , "Something creepy" , "Ballet-dancing costume" , "Wraith" , "RR" .)