Dog that's left on the bridge (7)
I believe the answer is:
spaniel
'dog' is the definition.
(I've seen this before)
'that's left on the bridge' is the wordplay.
'that's' becomes 'ie'.
'left' becomes 'l' (common abbreviation).
'on' says to put letters next to each other.
'the bridge' becomes 'span' ('span' can be a synonym of 'bridge'**).
'ie'+'l'='iel'
'iel' put after 'span' is 'SPANIEL'.
(Other definitions for spaniel that I've seen before include "Dog with long silky coat" , "Animal" , "[HOUND]" , "Springer- - -" , "Gundog; obsequious type" .)