Distance that is left for dog (7)
I believe the answer is:
spaniel
'for dog' is the definition.
(spaniel is a kind of dog)
'distance that is left' is the wordplay.
'distance' becomes 'span' (span is a kind of distance).
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'left' becomes 'l' (common abbreviation).
'span'+'ie'+'l'='SPANIEL'
(Other definitions for spaniel that I've seen before include "See 1 Across" , "Breed of dog" , "[HOUND]" , "Dog with long silky coat" , "See 13" .)