Lay in some vanilla ice cream (4)
I believe the answer is:
laic
'lay' is the definition.
(I know that lay can be written as laic)
'some vanilla ice cream' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'LAIC' is hidden in the letters of 'vanilla ice cream'.
'in' is the link.
(Other definitions for laic that I've seen before include "belonging to the people" , "Non-clergy" , "Of those not members of the clergy" , "non-professional" , "outside the church" .)