Leaves fellow changing oil to get on (7)
I believe the answer is:
foliage
'leaves' is the definition.
(I've seen this before)
'fellow changing oil to get on' is the wordplay.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'changing' indicates anagramming the letters.
'to get on' becomes 'age' ('age' can be a synonym of 'get on').
'oil' with letters rearranged gives 'oli'.
'f'+'oli'+'age'='FOLIAGE'
(Other definitions for foliage that I've seen before include "Mass of leaves" , "Leaves of tree or plant" , "Green leaves" , "Plant leaves collectively" , "(Decorative) leaves" .)