Knocks back strong liquor in study at the last minute (4)
I believe the answer is:
cram
'study at the last minute' is the definition.
(I've seen this in another clue)
'knocks back strong liquor' is the wordplay.
'knocks back' says the letters should be written backwards (I've seen 'knocking back' mean this).
'strong liquor' becomes 'marc' (I've seen this before).
'marc' in reverse letter order is 'CRAM'.
'in' acts as a link.
(Other definitions for cram that I've seen before include "Crowd or pack to capacity" , "Greedily eat" , "Revise hard" , "Stuff full" , "prepare for exam" .)