Catch part of a carol at Christmas (5)
I believe the answer is:
latch
'catch' is the definition.
(latch is a kind of catch)
'part of a carol at christmas' is the wordplay.
'part of' indicates a hidden word.
'LATCH' is hidden in the letters of 'carol at christmas'.
(Other definitions for latch that I've seen before include "Door securer" , "Bar to close" , "Door fastener" , "Device for opening door" , "Something to secure" .)