Lean or narrow (4)
I believe the answer is:
thin
I believe this is a double definition.
'lean' is the first definition.
(I know that lean can be written as thin)
'narrow' is the second definition.
(associated in meaning)
(Other definitions for thin that I've seen before include "With little thickness" , "Sparse; not dense" , "Having little width" , "Carrying little fat" , "Slender, slight" .)