what role does "a" play here
@candle from what's left of my secondary school French, "has/had"? some past tense variant of avoir...
@candle This is a passé composé sentence. "a" is the auxiliary verb "avoir"
@candle "canalisé" is only the past participe, it needs an auxiliary. ex: "Il a canalisé" : he channeled. "Il est canalisé" : he is channeled
@candle "a" is an auxiliary (basically it's the "avoir" verb, used as a grammatical tool. When combined with a "past participle" (here "canalisé") it allows you to form another tense (here, the "passé composé"). Those combined forms always convey an "achieved" notion. The action/process has been done and is finished.
@candle Does the last e in canalise wear an accent? Then it would mean "[..] has channelled"