Dangerous to include 1000 in US city in prayer (4,4)
I believe the answer is:
hail mary
'prayer' is the definition.
(Hail Mary is an example)
'dangerous to include 1000 in us city' is the wordplay.
'dangerous' becomes 'hairy' (I've seen this before**).
'to include' indicates putting letters inside.
'h000' becomes 'm' ('m' can be a synonym of 'h000').
'in' is an insertion indicator.
'us city' becomes 'la'.
'm' inserted within 'la' is 'lma'.
'hairy' going around 'lma' is 'HAIL MARY'.
'in' is the link.
(Other definitions for hail mary that I've seen before include "Prayer to the Virgin" , "Ave Maria" .)