The Spanish drinking your old kind of alcohol (5)
I believe the answer is:
ethyl
'kind of alcohol' is the definition.
(chemistry)
'the spanish drinking your old' is the wordplay.
'the spanish' becomes 'el' ('the' in Spanish).
'drinking' indicates putting letters inside.
'your old' becomes 'thy' ('thy' historically meant 'your').
'el' placed around 'thy' is 'ETHYL'.
(Other definitions for ethyl that I've seen before include "Alkyl radical, base of common alcohol" , "-- Alcohol; -- acetate" , "C2H5" , "compound" .)