Mixed dram containing whiskey put into drink that's a comfort at night (3,6)

'a comfort at night' is the definition.
I know nothing about this answer so I can't judge whether this works.

'mixed dram containing whiskey put into drink' is the wordplay.
'mixed' is an anagram indicator.
'containing' indicates putting letters inside.
'whiskey' becomes 'W' (alpha bravo charlie delta ...).
'put into' indicates putting letters inside.
'drink' becomes 'beer' (beer is a kind of drink).
'dram' with letters rearranged gives 'darm'.
'darm' placed around 'w' is 'dwarm'.
'dwarm' put inside 'beer' is 'BED-WARMER'.

'that's' is the link.

Can you help me to learn more?