Touch, lean on (4)
I believe the answer is:
abut
This clue is a double definition.
'touch' is the first definition.
(abutting is a kind of touching)
'lean on' is the second definition.
(I've seen this in another clue)
(Other definitions for abut that I've seen before include "Adjoin, border" , "Touch, lean on" , "Adjoin at one end" , "Touch upon" , "Touch (side of next building)" .)