A woman gets cocktail that'll keep her warm on a cold night (6)
I believe the answer is:
anorak
'that'll keep her warm on a cold night' is the definition.
The definition suggests a singular noun which matches the answer.
'a woman gets cocktail' is the wordplay.
'a' becomes 'an'.
'woman' becomes 'ora'.
'gets cocktail' becomes 'k' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'an'+'ora'+'k'='ANORAK'
Can you help me to learn more?
(Other definitions for anorak that I've seen before include "Jacket; nerd (colloq.)" , "geek" , "Dull person" , "Jacket for an obsessive?" , "Garment; studious person" .)