Most of the foam on stout in Ring (8)
I believe the answer is:
surround
'ring' is the definition.
('surround' can be a synonym of 'ring')
'most of the foam on stout' is the wordplay.
'most of' means to remove the last letter.
'the foam' becomes 'surf' (I've seen this before).
'on' means one lot of letters go next to another.
'stout' becomes 'round' (I've seen this before).
'surf' with its final letter removed is 'sur'.
'sur'+'round'='SURROUND'
'in' is the link.
(Other definitions for surround that I've seen before include "Encircle, fence in" , "Ring" , "Encompass" .)