Spoils trouser fabric, introducing drop of antique liqueur (10)
I believe the answer is:
maraschino
'liqueur' is the definition.
(I know that Maraschino is a type of liqueur)
'spoils trouser fabric introducing drop of antique' is the wordplay.
'spoils' becomes 'mars' ('mar' can be a synonym of 'spoil').
'trouser fabric' becomes 'chino' (I've seen this in another clue).
'introducing' is an insertion indicator (some letters introduced or inserted into others).
'drop of' suggests taking the first letters.
The initial letter of 'antique' is 'a'.
'mars'+'chino'='marschino'
'marschino' going around 'a' is 'MARASCHINO'.
(Another definition for maraschino that I've seen is " Harmonicas (anag) - cherry liqueur".)