Quick to secure edge in leadership (7)
I believe the answer is:
primacy
'leadership' is the definition.
(thesaurus)
'quick to secure edge' is the wordplay.
'quick' becomes 'pacy'.
'to secure' means one lot of letters goes inside another.
'edge' becomes 'rim' (rim is a kind of edge).
'pacy' placed around 'rim' is 'PRIMACY'.
'in' acts as a link.
(Other definitions for primacy that I've seen before include "Dominance" , "precedence" , "first place" .)