Key army corps almost crazy about hotel’s liqueur (5,2,6)
I believe the answer is:
creme de menthe
'liqueur' is the definition.
(creme de menthe is a kind of liqueur)
'key army corps almost crazy about hotel's' is the wordplay.
I cannot really understand how this works, but
'key' could be 'e' (I've seen this in other clues) and 'e' is present in the answer.
'about' could be 'c' (abbreviation for 'circa') and 'c' is present in the answer.
'hotel' could be 'h' (phonetic alphabet: alpha, bravo, charlie etc.) and 'h' is found within the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for creme de menthe that I've seen before include "Green liquid" , "Green peppermint-flavoured liqueur" , "spirit" , "Peppermint liqueur" , "Mint flavoured liqueur" .)