PM briefly drinking the Spanish sauce (6)
I believe the answer is:
relish
'sauce' is the definition.
(I know that relish is a type of sauce)
'pm briefly drinking the spanish' is the wordplay.
'pm briefly' becomes 'rish' (I am not sure about this - if you are sure you should believe this answer much more).
'drinking' indicates putting letters inside (inserted letters are consumed or drunk).
'the spanish' becomes 'el' ('the' in Spanish).
'rish' enclosing 'el' is 'RELISH'.
Can you help me to learn more?
(Other definitions for relish that I've seen before include "Gusto" , "appetizer?" , "Sauce or flavouring" , "Look forward to" , "what goes on food" .)