Investigate former leader of party's traditional knowledge (7)
I believe the answer is:
explore
'investigate' is the definition.
(exploring is a kind of investigating)
'former leader of party's traditional knowledge' is the wordplay.
'former' becomes 'ex'.
'leader of' says to take the initial letters.
'traditional knowledge' becomes 'lore' ('lore' can be a synonym of 'traditional knowledge').
The initial letter of 'partys' is 'p'.
'ex'+'p'+'lore'='EXPLORE'
(Other definitions for explore that I've seen before include "Travel through for purpose of discovery" , "Travel through an area to learn about it" , "Examine or investigate, new country or possibilities" , "Investigate for the purpose of discovery" , "Search and inquire into" .)