Question

Is this sentence a phrase or a clause

The thief creptas a jackal does

Answer 1

           The  thief  crept    as a jackal  does.

   This is a sentence.   there is a noun, verb, and a clause.

clause  --   as a jackal does.

Answer 2

A phrase may not have a subject or a verb.

A clause may have a subject or a verb.

So in this sentence 'a jackal does' contains a subject (jackal) and verb (does).

Hence it is a clause.