Families heading for Christmas on computer network (4)
I believe the answer is:
clan
'families heading' is the definition.
'clan' can be an answer for 'heading' (thesaurus). I am not sure about the 'families' bit.
'christmas on computer network' is the wordplay.
'christmas' becomes 'c' (this could be a standard abbreviation I've not previously seen).
'on' says to put letters next to each other.
'computer network' becomes 'lan' (abbreviation for local-area network).
'c'+'lan'='CLAN'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for clan that I've seen before include "Group with a tartan?" , "Tribe or collection of families under a cheiftain" , "People related by blood and marriage" , "Scots family grouping" , "Group of related families" .)