Our diplomacy works without even contributions from BoJo's party (5,5)

I believe the answer is:

plaid cymru

'party' is the definition.
(Welsh political party)

I don't understand how the remainder of the clue works.

(Other definitions for plaid cymru that I've seen before include "party in UK" , "party in Wales" , "Welsh political party" , "Welsh Nationalist party" .)

I've seen this clue in The Independent.

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