Long period of time before new leader (5)
I believe the answer is:
yearn
'long' is the definition.
('yearn' can be a synonym of 'long')
'period of time before new leader' is the wordplay.
'period of time' becomes 'year' (year is a kind of period of time**).
'before' says to put letters next to each other.
'leader' says to take the initial letters.
The first letter of 'new' is 'n'.
'year'+'n'='YEARN'
(Other definitions for yearn that I've seen before include "wish" , "Have a craving" , "Have an intense feeling of longing" , "Desire, want" , "Hanker" .)