...'Asia' perhaps, including start of great group (10)
I believe the answer is:
contingent
'great group' is the definition.
'contingent' can be an answer for 'group' (contingent is a kind of group). I'm not certain of the 'great' bit.
'asia perhaps including start' is the wordplay.
'asia perhaps' becomes 'continent' (asia is a kind of continent).
'including' is an insertion indicator.
'start' becomes 'g' (I can't justify this - if you can you should believe this answer much more).
'continent' placed around 'g' is 'CONTINGENT'.
'of' is the link.
Can you help me to learn more?
(Other definitions for contingent that I've seen before include "not necessary" , "Depending (on) - part of military force" , "uncertain" , "Company" , "party" .)