Member joining top celebrities: one sticking to the law (8)
I believe the answer is:
legalist
'one sticking to the law' is the definition.
(a legalist advocates following the law)
'member joining top celebrities' is the wordplay.
'member' becomes 'leg' (member can mean a limb).
'joining' says to put letters next to each other.
'top celebrities' becomes 'alist' (the A-list means very famous people).
'leg'+'alist'='LEGALIST'
(Other definitions for legalist that I've seen before include "Strict lawyer" , "One adhering to the detail of the law" .)