Old African colonel initially grinning as dull dignitaries all file in (7)
I believe the answer is:
gaddafi
'old african colonel' is the definition.
(Muammar Gaddafi, former leader of Libya)
'initially grinning as dull dignitaries all file in' is the wordplay.
'initially' suggests taking the first letters.
The initial letters of 'grinning as dull dignitaries all file in' is 'GADDAFI'.
(Other definitions for gaddafi that I've seen before include "deposed dictator" , "Luxury car" , "Libyan leader" .)