Old general I pass invading Indian city (8)
I believe the answer is:
agricola
'old general' is the definition.
(I've seen this before)
'i pass invading indian city' is the wordplay.
'pass' becomes 'col' (col is a term for a mountain pass).
'invading' is an insertion indicator.
'indian city' becomes 'agra' (city in India).
'i'+'col'='icol'
'icol' put into 'agra' is 'AGRICOLA'.
(Other definitions for agricola that I've seen before include "Ancient soldier" , "Old general" , "Roman general who conquered much of Britain" .)