Just start to simmer and make insinuations (6)
I believe the answer is:
simply
'just' is the definition.
(I know that just can be written as simply)
'start to simmer and make insinuations' is the wordplay.
'start to' indicates taking the first letters.
'and' says to put letters next to each other.
'make insinuations' becomes 'imply' (to imply something is to insinuate it).
The initial letter of 'simmer' is 's'.
's'+'imply'='SIMPLY'
(Other definitions for simply that I've seen before include "In a straightforward manner" , "Merely, just" , "Without fuss" .)