Talk a little covering compound (6)
I believe the answer is:
alkali
'compound' is the definition.
(I know that alkali is a type of salt)
'talk a little covering' is the wordplay.
'covering' says the answer is hidden in the clue.
'ALKALI' is hidden within 'talk a little'.
(Other definitions for alkali that I've seen before include "Acid-neutralising chemical" , "Substance such as lime or caustic soda" , "Compound like lime" , "Soluble compound that turns litmus paper blue" , "Substance with pH of over 7" .)