Circulate margarine, say (6)
I believe the answer is:
spread
I believe this clue is a double definition.
'circulate' is the first definition.
(spreading is a kind of circulating)
'margarine say' is the second definition.
(margarine is a kind of spread)
(Other definitions for spread that I've seen before include "Broaden - drapes (anag)" , "Scatter or distribute more thinly" , "Diffuse" , "Distribute or disperse widely" , "Rancher's property - sumptuous meal" .)