Left your leader following Bush Senior (7)
I believe the answer is:
elderly
'senior' is the definition.
(I know that senior can be written as elderly)
'left your leader following bush' is the wordplay.
'leader' suggests taking the first letters.
'following' says to put letters next to each other.
'bush' becomes 'elder' (elder is a kind of bush).
The first letters of 'left your' is 'ly'.
'ly' after 'elder' is 'ELDERLY'.
(Other definitions for elderly that I've seen before include "Quite old" , "Mature" , "Long in the tooth" , "Old or ageing" , "over the hill" .)