Keep scores holding a winter celebration (8)
I believe the answer is:
hogmanay
'winter celebration' is the definition.
'keep scores holding a' is the wordplay.
'keep' becomes 'hog'.
'scores' becomes 'many'.
'holding' is an insertion indicator.
'many' enclosing 'a' is 'manay'.
'hog'+'manay'='HOGMANAY'
(Other definitions for hogmanay that I've seen before include "New Year's Eve in Scotland" , "Scottish celebration framed in mahogany" , "New Year's Eve (Scots)" , "New Year's Eve in Glasgow" , "today" .)