Dog's range: that is a short length (7)
I believe the answer is:
spaniel
'dog's' is the definition.
(spaniel is a kind of dog)
'range that is a short length' is the wordplay.
'range' becomes 'span' (I've seen this before**).
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'a short' indicates taking the first letters.
The initial letter of 'length' is 'l'.
'span'+'ie'+'l'='SPANIEL'
(Other definitions for spaniel that I've seen before include "Alpines (anag)" , "See 1 Across" , "Animal" , "Droopy-eared dog" , "Type of dog" .)