Sirius tops the canine bill (7)
I believe the answer is:
dogstar
'sirius tops' is the definition.
I know nothing about this answer so I cannot tell whether this works.
'canine bill' is the wordplay.
'canine' becomes 'dog' (dog is a kind of canine).
'bill' becomes 'star' (I am not sure about this - if you are sure you should believe this answer much more).
'dog'+'star'='DOGSTAR'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for dogstar that I've seen before include "animal on TV?" , "This the brightest" , "Bright night light" .)