Screen showing part of festive illuminations (4)
I believe the answer is:
veil
'screen' is the definition.
(thesaurus)
'part of festive illuminations' is the wordplay.
'part of' says the answer is hidden in the clue.
'VEIL' is hidden within 'festive illuminations'.
'showing' is the link.
(Other definitions for veil that I've seen before include "Women's face covering of live kind" , "Cover, conceal" , "Curtain, disguise" , "Transparent face cover" , "Lacy facial covering" .)