Not quite saying what’ll reduce cholesterol (6)
I believe the answer is:
statin
'what'll reduce cholesterol' is the definition.
(I know that statins can reduce cholesterol)
'not quite saying' is the wordplay.
'not quite' means to remove the last letter (most but not all of the word).
'saying' becomes 'stating' ('state' can be a synonym of 'say').
'stating' with its last letter removed is 'STATIN'.
(Other definitions for statin that I've seen before include "Drug reducing cholesterol" , "Cholesterol-reducing drug" , "Drug given to reduce blood cholesterol" , "Cholesterol-lowering drug" .)