Prima facie the canal gate is broken (2,1,6)
I believe the answer is:
at a glance
'prima facie' is the definition.
(thesaurus)
'canal gate is broken' is the wordplay.
'is broken' is an anagram indicator.
'canal'+'gate'='canalgate'
'canalgate' with letters rearranged gives 'AT A GLANCE'.
'the' is the link.
(Other definitions for at a glance that I've seen before include "With just a look" , "immediately" .)