Nothing from speaker left tucking into two molluscs (7)
I believe the answer is:
nautili
'molluscs' is the definition.
(nautilus is a kind of mollusc)
'nothing from speaker left tucking into two' is the wordplay.
'nothing' becomes 'nought' ('nought' can be a synonym of 'zero').
'from speaker' shows a homophone (sound like).
'left' becomes 'l' (common abbreviation).
'tucking into' means one lot of letters goes inside another.
'two' becomes 'ii' ('II' can be a synonym of 'two').
'nought' sounds like 'naut'.
'l' placed within 'ii' is 'ili'.
'naut'+'ili'='NAUTILI'
(Other definitions for nautili that I've seen before include "creatures in the sea" , "Cephalopod molluscs" , "marine life" .)