Weapons going west in aeroplane's racks (7)
I believe the answer is:
arsenal
'weapons' is the definition.
(I've seen this before)
'going west in aeroplane's racks' is the wordplay.
'going west' shows that the letters should be reversed in order (letters heading to the west or left).
'in' indicates a hidden word.
'lanesra' is hidden within 'aeroplanes racks'.
'lanesra' in reverse letter order is 'ARSENAL'.
(Other definitions for arsenal that I've seen before include "munitions factory" , "Football club and military store" , "London premiership football team" , "Football club based at Emirates Stadium" , "Store of weapons or English soccer team." .)