Stop most of the group (4)
I believe the answer is:
bloc
'the group' is the definition.
The answer is an example.
'stop most' is the wordplay.
'stop' becomes 'block' (synonyms).
'most' means to remove the last letter.
'block' with its last letter taken away is 'BLOC'.
'of' is the link.
(Other definitions for bloc that I've seen before include "Combination of parties or countries" , "Alliance - coalition" , "Nations grouped for a purpose" , "Political grouping of countries" , "Political alliance" .)