Study in group including party leader (7)
I believe the answer is:
inspect
'study' is the definition.
(inspecting is a kind of studying)
'in group including party leader' is the wordplay.
'group' becomes 'sect' (I've seen this in other clues**).
'including' means one lot of letters goes inside another.
'party leader' becomes 'p' (I've seen this in other clues).
'sect' enclosing 'p' is 'spect'.
'in'+'spect'='INSPECT'
(Other definitions for inspect that I've seen before include "Check" , "Examine or survey" , "vet" , "Look at closely" , "Study" .)