British greasy fluid, i.e. stew (4)
I believe the answer is:
boil
'stew' is the definition.
(I've seen this in another clue)
'british greasy fluid i e' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in BBC).
'greasy fluid i e' becomes 'oil' (I can't justify this - if you can you should believe this answer much more).
'b'+'oil'='BOIL'
Can you help me to learn more?
(Other definitions for boil that I've seen before include "Eruption of the skin" , "let off steam" , "Cook in hot water" , "Seethe - painful swelling" , "Painful sore" .)