Surrounded by a number in support (4)
I believe the answer is:
amid
'surrounded by' is the definition.
(I've seen this before)
'a number in support' is the wordplay.
'number in support' becomes 'mid' (I can't explain this - if you can you should believe this answer much more).
'a'+'mid'='AMID'
Can you help me to learn more?
(Other definitions for amid that I've seen before include "'See . . . . the winter's snow' (carol)" , "In the course of" , "Amongst" , "Within" , "In the middle of" .)