Arms trade leaders entertained by numerous delegates (8)
I believe the answer is:
legation
'delegates' is the definition.
'arms trade leaders entertained by numerous' is the wordplay.
'leaders' suggests taking the first letters.
'entertained by' is an insertion indicator (I've seen this in other clues).
'numerous' becomes 'legion'.
The initial letters of 'arms trade' is 'at'.
'at' placed within 'legion' is 'LEGATION'.
(Other definitions for legation that I've seen before include "Embassy" , "Official residence of diplomat and staff" , "A long tie (anag.)" , "Diplomatic minister and staff, and their residence" , "Diplomatic group or mission" .)