Darling's cross turning up on threshold (8)
I believe the answer is:
doorstep
'threshold' is the definition.
('doorstep' can be a synonym of 'threshold')
'darling's cross turning up' is the wordplay.
'darling's' becomes 'pets' ('pet' can be a synonym of 'darling').
'cross' becomes 'rood' (term for a crucifix).
'turning up' is a reversal indicator.
'pets'+'rood'='petsrood'
'petsrood' reversed gives 'DOORSTEP'.
'on' acts as a link.
(Other definitions for doorstep that I've seen before include "Torpedos (anag.)" , "big piece of bread" , "Try some canvassing" , "Large slice of bread?" , "Threshold stair" .)