Crowd round Missouri bureau head (3)
I believe the answer is:
mob
'crowd round' is the definition.
(I've seen this before)
'missouri bureau head' is the wordplay.
'missouri' becomes 'mo'.
'head' suggests taking the first letters.
The first letter of 'bureau' is 'b'.
'mo'+'b'='MOB'
(Other definitions for mob that I've seen before include "Kind of cap" , "Rabble" , "Crime syndicate or disorderly crowd" , "Large, disorderly crowd" , "An unruly or uncontrolled gang" .)