Fire about ten main people finally, in addition (6)
I believe the answer is:
annexe
'addition' is the definition.
(annexe is a kind of addition)
'fire about ten main people finally' is the wordplay.
'fire' becomes 'axe' (I've seen this before**).
'about' is an insertion indicator.
'finally' suggests the final letters.
The last letters of 'ten main people' are 'nne'.
'axe' enclosing 'nne' is 'ANNEXE'.
'in' acts as a link.
(Other definitions for annexe that I've seen before include "Appropriate into one's territory" , "Extension, supplement" , "Additional building" , "Wing - extension" , "Building joined to another" .)