Cast aspersions, briefly, but swallowed it to keep cold at bay (8)
I believe the answer is:
insulate
'cast' is the definition.
Although both the answer and definition are verbs in their base form, I don't see how one could define the other.
'aspersions briefly but swallowed it to keep cold at bay' is the wordplay.
I cannot quite understand how this works, but
'swallowed' could be 'ate' (swallow can mean to eat) and 'ate' is found within the answer.
'at' could be 'in' (synonymous in some cases - eg at school, in school) and 'in' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for insulate that I've seen before include "Protect (from, eg, heat)" , "Cover with material to prevent loss of heat" , "Lag" , "Cover something to prevent loss of heat" , "Lean suit (anag.)" .)