Now in her childlike eyes
You see the beauty there
You know it was always there
And you need no longer wear a disguise
The "there" of "You know it was always there" is a perfect rhyme with the "wear" of "And you need no longer wear," and those two phrases have the same number of syllables (seven), so - as far as rhyme and syllable count are concerned - "a disguise" isn't necessary.* There's even a bit of a pause in Micky's vocal between "no longer wear" and "a disguise," which seems to underscore that it's poetically unnecessary.
In the same way that the phrase "a disguise" isn't necessary to fill in some more syllables of that line or rhyme with the previous line, the lyric itself is also saying - a bit more literally - that a disguise isn't necessary.
In the same way that the phrase "a disguise" isn't necessary to fill in some more syllables of that line or rhyme with the previous line, the lyric itself is also saying - a bit more literally - that a disguise isn't necessary.
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*Of course, in order to make sense, that line does need "a disguise" because - even though it's an infinitive here - wear (in this sense) is a transitive verb and needs an object.