could this be a clause

[Ashish1354]

Hermione wanted her name changed because it was hard to pronounce.

Please explain why is above bold face text a clause and not a phrase.

I thought it is a phrase because it has no subject and now after looking at answer i am confused.

[Mister Micawber]

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It is a clause. It has a subject, 'it' and a verb, 'was'.
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Native English teacher at Mister Micawber's