Bullet case in farm vehicle by narrow hilltop (9)
I believe the answer is:
cartridge
'bullet case' is the definition.
(I've seen this before)
'farm vehicle by narrow hilltop' is the wordplay.
'farm vehicle' becomes 'cart' (I've seen this before).
'by' is a charade indicator (letters next to each other).
'narrow hilltop' becomes 'ridge' (I've seen this before).
'cart'+'ridge'='CARTRIDGE'
'in' is the link.
(Other definitions for cartridge that I've seen before include "holds a lot of ink" , "Sort of paper" , "shot put in it" , "Bullet's casing" , "round" .)