Part of leg found by excavation party (7)
I believe the answer is:
shindig
'party' is the definition.
(I've seen this before)
'part of leg found by excavation' is the wordplay.
'part of leg' becomes 'shin' ('shin' is part of 'leg').
'found by' says to put letters next to each other.
'excavation' becomes 'dig' ('dig' can be a synonym of 'excavation').
'shin'+'dig'='SHINDIG'
(Other definitions for shindig that I've seen before include "Noisy disturbance" , "Large and noisy party or quarrel" , "Hooley" , "Lively celebration (informal)" , "commotion" .)