Pure dairy product British avoided (5)
I believe the answer is:
utter
'pure' is the definition.
('utter' can be a synonym of 'pure')
'dairy product british avoided' is the wordplay.
'dairy product' becomes 'butter' (butter is a kind of dairy product).
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'avoided' indicates named letters should be taken away.
'butter' with 'b' taken away is 'UTTER'.
(Other definitions for utter that I've seen before include "in toto" , "Total - speak" , "State - unqualified - rank" , "mouth" , "Give tongue to" .)