Knocked back most of milk, beefcake and cheese (9)
I believe the answer is:
limburger
'cheese' is the definition.
(I've seen this before)
'knocked back most of milk beefcake' is the wordplay.
'knocked back' says the letters should be written backwards.
'most of' means to remove the last letter.
'beefcake' becomes 'burger' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'milk' with its final letter removed is 'mil'.
'mil' reversed gives 'lim'.
'lim'+'burger'='LIMBURGER'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for limburger that I've seen before include "something very smelly will result" , "Soft Belgian cheese" .)