Some slimmers eat duck (7)
I believe the answer is:
immerse
'duck' is the definition.
(I've seen this before)
'some slimmers eat' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'IMMERSE' is hidden within 'slimmers eat'.
(Other definitions for immerse that I've seen before include "Absorb" , "duck" , "Plunge deep into liquid" , "Submerge in water or liquid" , "Submerge in water as once for baptism" .)