Central America has a cathedral city, depend on it! (4)
I believe the answer is:
rely
'depend on it' is the definition.
(I've seen this before)
'central america has a cathedral city' is the wordplay.
'central' says to take the centre.
'has' means one lot of letters go next to another.
'a cathedral city' becomes 'Ely' (English city with a cathedral).
The middle letter of 'america' is 'r'.
'r'+'ely'='RELY'
(Other definitions for rely that I've seen before include "Be dependent" , "Old rally" , "Bank (on someone)" , "Run and see" , "Depend or lean on" .)